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Solid-Earth geophysics in Scandinavia
A t r i a l in the Korsn~ls lead a r e a showed that c h e m i c a l a n a l y s e s of the f i n e s t f r a c t i o n s of till m a y give s u p p l e m e n t a r y i n f o r m a t i o n in the boulder t r a i n hunting. T h e d i f f e r e n c e s in the b a s e m e t a l content of peat a s h led M. Salmi to apply t h i s o b s e r v a t i o n to ore p r o s p e c t i n g . A c c o r d i n g to s o m e t r i a l w o r k s , t h e r e s e e m s to be a c o r r e l a t i o n between the b e d r o c k and the peat a s h . At l e a s t in F i n l a n d and in Norway, p e a t - c h e m i c a l p r o s p e c t i n g is continuously used. G e o c h e m i s t s in Scandinavian c o u n t r i e s c o o p e r a t e t o g e t h e r c l o s e l y . E v e r y s e c o n d y e a r the g e o l o g i s t s have a w i n t e r m e e t i n g in which the g e o c h e m i s t s h a v e t h e i r own section. The p a p e r s a r e p u b l i s h e d e i t h e r in the Survey b u l l e t i n s or in the s e r i e s of geological s o c i e t i e s of each country. T h e r e is no s p e c i a l p e r i o d i c a l for g e o c h e m i s t r y . In the n e a r f u t u r e the m a i n t r e n d in Scandinavian g e o c h e m i s t r y will probably be in the application of ore p r o s p e c t i n g and geochronology. T h i s is done e x t e n s i v e l y in each country by g o v e r n m e n t a g e n c i e s and p r i v a t e m i n i n g c o m p a n i e s . A. MIKKOLA
Solid-Earth Geophysics in Scandinavia GEOMAGNETISM IN SCANDINAVIA Only a b r i e f outline of s o m e of the p r a c t i c a l a s p e c t s of g e o m a g n e t i s m in Scandinavia can be given h e r e . R e s e a r c h work is p u r s u e d at s o m e of the m a g n e t i c o b s e r v a t o r i e s m e n t i o n e d below and by s c a t t e r e d g r o u p s , e.g., at the U n i v e r s i t y of B e r g e n , Norwegian I n s t i t u t e of C o s m i c P h y s i c s , Royal Swedish I n s t i t u t e of Technology and the K i r u n a Geophysical O b s e r v a t o r y . The p r i n c i p a l f i e l d s of i n v e s t i g a t i o n p e r t a i n to a r c h a e o - and p a l a e o m a g n e t i s m , c r u s t conductivity, r a p i d v a r i a t i o n s , a u r o r a l p h e n o m e n a , u p p e r a t m o s p h e r e and m a g n e t o s p h e r e . I n t e r - N o r d i c cooperation in g e o m a g n e t i s m h a s always been noteworthy. Two of the m o s t n o table e x a m p l e s a r e : (1) T h e C h a r t s of A v e r a g e G e o m a g n e t i c E l e m e n t s D, H and Z 1955.0 for D e n m a r k , Finland, Norway, Sweden, which w e r e p u b l i s h e d jointly by the four c o u n t r i e s ; (2) The p a r t i c i p a t i o n in the a e r o m a g n e t i c s u r v e y of Scandinavia p e r f o r m e d in the a u t u m n of 1965 by the Dominion O b s e r v a t o r y , Ottawa, with 35 k m line spacing. Dennzark
The g e o m a g n e t i c work is s u p e r v i s e d by the D a n i s h M e t e o r o l o g i c a l Institute. O b s e r v a t o r i e s . R e g u l a r o b s e r v a t i o n s began at the Copenhagen O b s e r v a t o r y in 1891. It w a s r e placed by Rude Skov in 1906. Rude Skov h a s , for m a n y y e a r s , been a s t a n d a r d o b s e r v a t o r y f r o m which the o b s e r v a t o r i e s in the o t h e r Nordic c o u n t r i e s have o b t a i n e d t h e i r a b s o l u t e field values. Since the d e v e l o p m e n t of the c e l e b r a t e d La Cour s y s t e m of r e c o r d i n g and " s e m i - a b s o l u t e " m a g netic i n s t r u m e n t s , D e n m a r k h a s e x p o r t e d - on a s t r i c t n o n - p r o f i t b a s i s - m a g n e t i c i n s t r u m e n t s a r o u n d the world. Rude Skov is the b a s i s of all m a g n e t i c work in Greenland. Absolute s t a n d a r d : c l a s s i c a l i n s t r u m e n t s and proton m a g n e t o m e t e r . Godhavn, G r e e n l a n d , s t a r t e d in 1926, Thule, G r e e n l a n d , h a s occupied its p r e s e n t s i t e s i n c e 1955. All o b s e r v a t o r i e s have n o r m a l m a g n e t o g r a p h s and La Cour quickrun. S u r v e y s . A g e n e r a l m a g n e t i c s u r v e y was m a d e between 1890 and 1905. Since then s p o r a d i c s u r v e y s have been m a d e of s e l e c t e d a r e a s . A net of about ten s e c u l a r s t a t i o n s is r e o c c u p i e d e v e r y five y e a r s . In the s u m m e r of 1965, a s u r v e y was m a d e of the west c o a s t of Greenland. About 50 s t a t i o n s w e r e m e a s u r e d between l a t i t u d e s of 61°N and 75°N. F i~l la nd O b s e r v a t o r i e s . At Nurmij~irvi, u n d e r the s u p e r v i s i o n of the F i n n i s h M e t e o r o l o g i c a l Office, o b s e r v a t i o n s Started in 1953 u s i n g the n o r m a l r e c o r d e r , La Cour q u i c k r u n and e a r t h c u r r e n t s for one component ( r e s o l u t i o n 1 sec). Absolute s t a n d a r d is b a s e d on the proton m a g n e t o m e t e r and Nordic c o m p a r i s o n s . Sodankyl~i is s u p e r v i s e d by the F i n n i s h A c a d e m y of Science. It o p e r a t e d f r o m 1914 to 1944. A f t e r i n t e r r u p t i o n due to w a r d e s t r u c t i o n , r e g u l a r r e c o r d i n g s t a r t e d again in 1946 u s i n g the n o r m a l r e c o r d e r , La Cour q u i c k r u n , e a r t h c u r r e n t s and the G5ttingen pulsation r e c o r d e r . Absolute v a l u e s a r e obtained t h r o u g h c o m p a r i s o n s .
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Surveys. A g e n e r a l magnetic ground survey f r o m about 1,000 stations was made in 1910-1928. About 40 s e c u l a r stations have been reoccupied at r e g u l a r i n t e r v a l s (since 1950, almost yearly). Supervision: the Finnish Meteorological Office. About 80~ of Finland has been c o v e r e d by a lowaltitude (150 m) a e r o m a g n e t i c survey of the totaI intensity, with line spacin~ of 400 m ( s u p e r vision: the Geological Survey of Finland). Norway Observatories. Domb~ls is p r e s e n t l y under the supervision of the Geophysical Institute of the University of Bergen. O b s e r v a t i o n s began in 1916. Absolute values have been ,riven s i n c e 1952 when the new site was occupied. The n o r m a l r e c o r d e r is used. Absolute s t a n d a r d is d e r i v e d through Nordic c o m p a r i s o n s . T r o m s 5 (the Norwegian Institute of Cosmic P h y s i c s ) s t a r t e d in 1930 using the n o r m a l r e c o r d e r and the G6ttingen pulsation r e c o r d e r . Absolute values are d e r i v e d through c o m p a r i s o n s . The staff of T r o m s 5 also o p e r a t e s the magnetic station on Bear Island. Surveys. Through the joint effort of the Hydrographic Office of Norway and the Magnetic Bureau in Bergen, a net of 120 s e c u l a r stations was m e a s u r e d and reduced to epoch 1941.5. Another net of about 1,000 stations was reduced to 1947.5. In addition, the Hydrographic Office has issued four m a p s of declination covering s o m e coastal w a t e r s of outstanding anomalies. The Geographical Survey of Norway also c a r r i e d out a large n u m b e r of magnetic o b s e r v a t i o n s in 1941-1957. In 1965, the whoIe survey work in Norway was taken over by the Geographical S u r vey Office. S c a t t e r e d o b s e r v a t i o n s along the coast of Svalbard have been made by the Norwegian Polar Institute (Norsk P o l a r Institute) as well as by Swedish and other foreign expeditions. Sweden Observatories. At Lov5 (the Swedish Board of Shipping and Navigation) o b s e r v a t i o n s began in 1927. Normal r e c o r d e r s and L a Cour quickrun are used. Absolute standard: proton m a g n e t o m e t e r and Nordic c o m p a r i s o n s . An auxiliary station, EnkSping, operating a Gbttingen pulsation r e c o r d e r , began r e c o r d i n g in 1963. Abisko (under joint s u p e r v i s i o n of the Board of Shipping and the Royal S w e d i s h / ~ c a d e m y of Sciences) has been recording, with i n t e r r u p t i o n s , since 1921 using n o r m a l r e c o r d e r s and part of the t i m e , La Cour quickrun. Absolute s t a n d a r d is reached by c o m p a r i s o n s . Kiruna (the Royal Swedish Academy of Sciences) began magnetic r e c o r d i n g about 1950, mostly as a complement to other e x p e r i m e n t s at the Geophysical O b s e r v a t o r y . P r e s e n t equipment includes normal r e c o r d e r s , GSttingen pulsation r e c o r d e r , Bould.er type r e cording in audio and subandio frequency range, e a r t h c u r r e n t s . An automatic s y s t e m of obtaining magnetic data in digital form has o p e r a t e d since 1965. Absolute values are obtained through c o m p a r i s o n s . Surveys. A number of o b s e r v a t i o n s along the coasts of Sweden and in surrounding w a t e r s have been p e r f o r m e d since about 1913. The s h i p - b o r n e s u r v e y s have largely been a joint effort by Sweden and Finland. A g e n e r a l survey (about 2,100 stations) was made in 1928-1934 by the Swedish Geological Survey. One net of about one hundred s e c u l a r stations e x i s t s since 1928 and another, of ten stations, since 1953 (the Swedish Board of Shipping and Navigation). Availability of geomagnetic data f o r Scandinavia Yearbooks giving monthlytabulations of mean hourly values in t h r e e components, annual mean values, C and K indices, etc., a r e i s s u e d r e g u l a r l y for the following o b s e r v a t o r i e s : Rude Skov, Godhavn, Thule, Nurmij~irvi, Sodankyl~i, DomNts, T r o m s S , LovS, Abisko, and Kiruna. Information r e g a r d i n g yearbooks, other publications, and magnetic c h a r t s can be obtained through the Swedish Board of Shipping and Navigation, Geomagnetic Section, Stockholm 27, Sweden. F. E L E M A N
GRAVIMETRY IN SCANDINAVIA
Gravirnetric observations on land
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T h e r e is a tradition of g r a v i m e t r i c work in Scandinavia. S e r i e s of pendulum o b s e r v a t i o n s w e r e undertaken in all the Scandinavian countries at the end of the last century and the i n v e s tigations continued until the t h i r t i e s of this century. A special survey was c a r r i e d out by the
Baltic Geodetic C o m m i s s i o n : studies of the pendulum m e a s u r e m e n t s , t h e i r c o r r e c t i o n s , and o t h e r f a c t o r s influencing the o b s e r v a t i o n s w e r e p e r f o r m e d at s e v e r a l places. It may also be mentioned that an investigation of the g r a v i m e t r i c t i e s between Copenhagen, the o t h e r Scandinavian capitals and a s e r i e s of European pendulum base stations was c a r r i e d out by N~rlund in the middle of the n i n e t e e n - t h i r t i e s . Scandinavia has also contributed to the development of m o d e r n g r a v i m e t e r s . At the beginning of this century, Ising c o n s t r u c t e d his f i r s t g r a v i m e t e r . It is only r e g r e t t a b l e that other work p r e v e n t e d Ising f r o m spending m o r e t i m e on this project. L a t e r on, g r a v i m e t e r s w e r e cons t r u c t e d by Lindblad and G. Malmqvist (the Boliden G r a v i m e t e r ) , and by Ndrgaard. The l a t t e r contributed a s e r i e s of different types which have been in use in s e v e r a l c o u n t r i e s a l l o v e r the world until recent y e a r s . Denmark
Due to the easy topography in Denmark, it has been a relatively easy task to produce topogra@hic m a p s ot the scale 1:20,000. T h e r e f o r e , it is not s u r p r i s i n g that the g r a v i m e t r i c net is v e r y dense: the distance between the g r a v i m e t r i c stations is not m o r e than 1.5 km and in many c a s e s l e s s than 1 kin. M e a s u r e m e n t s have been c a r r i e d out all over Denmark, including the s m a l l islands. Most of the r e s u l t s have been published by the Danish Geodetic Institute (Dansk Geoteknisk Institut), which has been r e s p o n s i b l e for the g r a v i m e t r i c work. The re/naining p o r tion of the o b s e r v a t i o n s is in the p r o c e s s of being published. In r e c e n t y e a r s , Aarhus U n i v e r s i t y has taken up detailed g r a v i m e t r i c studies in .connection with g e o p h y s i c a l - g e o l o g i c a l p r o b l e m s , e.g., t e c t o n i c s of salt domes, geological s t r u c t u r e s . In the F a r o e s , the f i r s t g r a v i m e t r i c s u r v e y was p e r f o r m e d by the Geodetic Institute in 1959 and another m o r e detailed s u r v e y was executed tn 1964. The Geodetic Institute has also u n d e r taken g r a v i m e t r i c m e a s u r e m e n t s in Greenland since 1950. Most of the r e s u l t s have been published. Finland
Finland was the f i r s t of the Scandinavian countries to publish a complete g r a v i m e t r i c map. The net is dense and the stations a r e equally d i s t r i b u t e d o v e r the country. However, the m o s t important contribution to gravity f r o m Finland is the work c a r r i e d out at the I s o s t a t i c Institute. Since the e s t a b l i s h m e n t 6f the institute (in 1938) up to now, 50 publications have been made. It also d e s e r v e s mention that the founder and d i r e c t o r of the institute, W.W. Heiskanen, b e s i d e s being d i r e c t o r of the Finnish Geodetic Institute, has been the leading p e r s o n in the e s t a b l i s h m e n t of the Ohio State University Institute for Geodesy, P h o t o g r a m m e t r y , and Cartography, f r o m which many valuable g r a v i m e t r i c p a p e r s have been published in r e c e n t years. Another contribution to g r a v i m e t r i c r e s e a r c h f r o m Finland is the relationship between gravity and the uplift of Scandinavia. Norway and Sweden
G r a v i m e t r i c field work in Norway andSweden is m o r e difficult due to the difficult topography. G r a v i m e t r i c m a p s of t h e s e c o u n t r i e s exist, but the spacing b e t w e e n t h e stations is very variable, e s p e c i a l l y in Norway, w h e r e stations in the mountain a r e a s a r e very s p a r s e . The m e a s u r e m e n t s r e p o r t e d f r o m Finland, Norway, and Sweden have been c a r r i e d out by the Geodetic Institutes and the Geographical Survey of Norway and the Geographical Survey Office of Sweden, r e s p e c t i v e l y . B e s i d e s , a s e r i e s of very detailed m e a s u r e m e n t s a r e being c a r r i e d out by p r o s p e c t i n g companies and g o v e r n m e n t a l agencies such as the Geological Surveys o r the u n i v e r s i t i e s . T h e s e s u r v e y s are tied into the geodetic s y s t e m s . Iceland
In Iceland, t h e D a n i s h G e o d e t i c Institute p e r f o r m e d a s e r i e s of pendulum o b s e r v a t i o n s in 1900. In the n i n e t e e n - t h i r t i e s , a G e r m a n expedition e s t a b l i s h e d a few pendulum s t a t i o n s while a detailed s u r v e y by m e a n s of g r a v i m e t e r s was undertaken by E i n a r s o n in 1950-1954. The r e s u l t s which w e r e published in 1954 have contributed to the geophysical-geologicai h i s t o r y of Iceland. G r a v i t y o b s e r v a t i o n s at s e a
So f a r only g r a v i m e t r i c o b s e r v a t i o n s of land a r e a s have been mentioned. However, Scandinavia has been active in s e a - g r a v i t y r e s e a r c h also. Of the t h r e e existing Vening Meinesz pendulums, one set belongs to the Danish Geodetic Institute. M e a s u r e m e n t s by m e a n s of this i n s t r u m e n t have been p e r f o r m e d by the Norwegian Geodetic Institute along the Norwegian Atlantic coast. The in-
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Alll
TECTONOPHYSICS International Journal of Geotectonics and the Geology and Physics of the Interior of the Earth SPECIAL ISS~JE ON EUROPEAN EARTHQUAKE MECHANISMS Edited by A.R. R i t s e m a
E d i t o r i a l - Earthquake m e c h a n i s m s : a European survey CA.R. Ritsema, De Bilt, The Netherlands) P o s s i b i l i t e s of determination of values of s t r e s s acting in earthquake foci (A.V. Vvedenskaya, Moscow, U.S.S.R.) On plastic deformations within the earthquake focus (K.V. Pshennikov, Irkutsk, U.S.S.R.) Computer work and mechanism studies (R.E. Ibgram, S.J., Dublin, Ireland) The focal mechanism of earthquakes in the southern coast of the Iberian Peninsula CA. Udias, S.J., Frankfort/Main, Germany) Computer determinations for the fault-plane solutions in and near Anatolia (N. Canitez and S. Balamir Tjcer, Istanbul, Turkey) On the use of surface waves in earthquake mechanism studies Cabstract) (A. Beu-Menahem, Rehovoth, Israel) Mechanisms of European earthquakes CA.R. Ritsema, De Bilt, The Netherlands) Rezente vertikale Erdkrustenbewegungen in Europa (L. Hiersemann, Halle/Saale, Germany) Synthetic seismic pulses from propagating faults (abstract) (B. Berekhemer and K.H. Jacob, Frankfort/Main, Germany) Fault-plane solutions of earthquakes in Baden-Wiirtemberg (abstract) (G. Schneider, R. Schick and H. Berekhemer, Stuttgart, Germany) Bibliography of recent crustal movements in Europe (L. Hiersemann, Halle/Saale, Germany)
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Tectonophysics
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s t r u m e n t h a s a l s o b e e n emlSloyed in Sweden. T h e F i n n s h a v e c a r r i e d out m e a s u r e m e n t s in t h e B a l t i c S e a a n d in t h e A r c t i c S e a by m e a n s of a b o t t o m g r a v i m e t e r , w h i l e U p p s a l a U n i v e r s i t y , S w e d e n , in a s i m i l a r way, h a s s t u d i e d a s p e c i a l r e g i o n in t h e B a l t i c Sea. R e c e n t l y , t h e D a n i s h G e o d e t i c I n s t i t u t e p u r c h a s e d an A s k a n i a s u r f a c e - s h i p g r a v i m e t e r a n d e x e c u t e d m e a s u r e m e n t s in t h e D a n i s h w a t e r s a s w e l l a s in t h e G r e e n l a n d Sea. In c o n c l u s i o n , it m u s t be s t a t e d t h a t e v e n if m o r e d e t a i l e d g r a v i m e t r i c s t u d i e s a r e n e e d e d , S c a n d i n a v i a , o r r a t h e r t h e N o r d i c c o u n t r i e s , a r e r e l a t i v e l y w e l l s u p p l i e d w i t h g r a v i m e t r i c data. S. SAXOV
S E I S M O L O G Y IN SCANDINAVIA
History of Seismology in Scandinavia W h e n , in 1899, r e c o r d i n g of t e l e s e i s m i c e v e n t s w a s f o u n d to be p o s s i b l e , a r i c h s c i e n t i f i c and t e c h n i c a l d e v e l o p m e n t b e g a n all o v e r t h e w o r l d w h i c h r e v e a l e d u n e x p e c t e d f a c t s about e a r t h q u a k e s a n d t h e e a r t h ' s i n t e r i o r . In s c i e n c e , o b s e r v a t i o n s a r e b e t t e r t h a n s p e c u l a t i o n s a s f o u n d a t i o n s f o r r e s u l t s , a n d in t h e e a s e of s e i s m o l o g y , o b s e r v a t i o n s m e a n e s t a b l i s h m e n t of s e i s m o graph stations. In S c a n d i n a v i a , t h e f i r s t s t a t i o n s w e r e e s t a b l i s h e d in 1904. In t h i s y e a r a o n e - c o m p o n e n t B o s c h s e i s m o g r a p h w a s put into o p e r a t i o n in B e r g e n ( N o r w a y ) a n d a t w o - c o m p o n e n t W i e c h e r t . H o r i z o n t a l in U p p s a l a (Sweden). Soon a f t e r , two m o r e s t a t i o n s followed: R e y k j a v i k ( I c e l a n d ) in 1909 a n d D i s c o I s l a n d ( G r e e n l a n d , o p e r a t e d f r o m D e n m a r k ) in 1910. T h e F i r s t W o r l d W a r r e t a r d e d f u r t h e r d e v e l o p m e n t , but in t h e y e a r s a f t e r t h e w a r , w o r k w a s t a k e n up a g a i n : H e l s i n k i ( F i n l a n d ) s t a r t e d o p e r a t i n g in 1924, C o p e n h a g e n ( D e n m a r k ) in 1927, a n d t h e G r e e n l a n d s t a t i o n s S c o r e s b y s u n d and I v i g t u t in 1928 and 1929. T h e D i s c o I s l a n d s t a t i o n w a s c l o s e d down a l t e r a few y,~ars and t h e I v i g t u t s t a t i o n in 1960; all t h e r e m a i n i n g s t a t i o n s a r e s t i l l o p e r a t i n g . T h e d e v e l o p m e n t of s e i s m o l o g y c o v e r s a wide field: f r o m t h e s i m p l e h o r i z o n t a l p e n d u l u m o v e r t h e W i e c h e r t s o r M a i n k a s ( s o m e of w h i c h a r e o p e r a t i n g t o d a y ) to t h e m o r e s o p h i s t i c a t e d e l e c t r o m a g n e t i c i n s t r u m e n t s of t h e G a l i t z i n type. In a p e r i o d c o v e r i n g a few y e a r s b e f o r e to s o m e y e a r s a f t e r t h e S e c o n d W o r l d W a r , m o s t of t h e s t a t i o n s w e r e e q u i p p e d w i t h s h o r t - p e r i o d v e r t i c a l s , t h e s e s e i s m o g r a p h s h a v i n g p r o v e d to be so v e r y u s e f u l f o r p r e c i s e r e a d i n g of P - w a v e s . At t h e s a m e t i m e , m a n y m o r e s t a t i o n s w e r e e s t a b l i s h e d . In s o m e of t h e m t h e e q u i p m e n t w a s r a t h e r s p a r s e , in o t h e r s m o r e a d v a n c e d , but m o s t of t h e m w e r e r u n n i n g an S P Z - i n s t r u m e n t . T h e n e x t w a v e of " r e - e q u i p m e n t " s e t in w h e n t h e W o r l d - W i d e S e i s m o g r a p h S y s t e m N e t w o r k w a s e s t a b l i s h e d by t h e U.S. C o a s t and G e o d e t i c S u r v e y d u r i n g t h e y e a r s 1961-1963. At t h e p r e s e n t t i m e , s t a n d a r d i n s t r u m e n t s of t h i s t y p e a r e in o p e r a t i o n at t h r e e G r e e n l a n d i c s t a t i o n s a n d at f i v e s t a t i o n s in S c a n d i n a v i a , p a r t l y at old s t a t i o n s t o g e t h e r with t h e p r e v i o u s i n s t r u m e n t a t i o n , p a r t l y at s t a t i o n s e s t a b l i s h e d ad hoc. O n e of t h e n e w e s t a d v a n c e s w i t h i n i n s t r u m e n t a l s e i s m o l o g y i s t h e u s e of s e i s m o g r a p h s a r r a y s . H o w e v e r , e v e n a s m a l l s i z e a r r a y i s a r a t h e r e x p e n s i v e i n s t r u m e n t to r u n . T h e r e f o r e , i n t e r N o r d i c d i s c u s s i o n s h a v e t a k e n p l a c e in o r d e r to d i s c o v e r how t h e f o r c e s m a y be j o i n e d in t h e b e s t m a n n e r . At t h r e e o r f o u r l o c a l i t i e s within S c a n d i n a v i a ( i n c l u d i n g G r e e n l a n d ) e x p e r i m e n t a l array stations have been established.
Seismology today T o d a y t h e N o r d i c c o u n t r i e s a r e r u n n i n g a b o u t 25 s e i s m o g r a p h s t a t i o n s . T h i s d e n s e n e t w o r k m e a n s t h a t S c a n d i n a v i a h a s a c o v e r i n g w e l l up to an i n t e r n a t i o n a l s t a n d a r d , a s f a r a s t e l e s e i s m i c r e c o r d i n g i s c o n c e r n e d . H o w e v e r , e v e n if t h e s e i s m i c i t y in all t h e c o u n t r i e s in q u e s t i o n i s s m a l l , m i n o r e v e n t s m a y o c c u r . In I c e l a n d , s u c h e v e n t s a r e v e r y f r e q u e n t . T h e A r c t i c r e g i o n s a l s o a p p e a r to be t h e s i t e of m a n y s m a l l e a r t h q u a k e s . E v e n in t h e a r e a s w i t h a m i n i m u m of s e i s m i c i t y D e n m a r k a n d s o m e p a r t s of F i n l a n d a n d N o r w a y - e a r t h q u a k e s a r e not e n t i r e l y a b s e n t . T h e s e s m a l l e v e n t s m a y be of g r e a t i n t e r e s t f r o m a s c i e n t i f i c p o i n t of view, but it i s d i f f i c u l t to s u b j e c t t h e m to a c o m p r e h e n s i v e s t u d y by m e a n s of t h e e x i s t i n g n e t of s t a t i o n s . T h e r e f o r e , all t h e c o u n t r i e s in q u e s t i o n a r e w o r k i n g f o r t h e e s t a b l i s h m e n t of a d e n s e r n e t of l o c a l s t a t i o n s . It s h o u l d a l s o be m e n t i o n e d t h a t i n v e s t i g a t i o n s on t h e s t r u c t u r e of t h e c r u s t a n d u p p e r m a n t l e h a v e b e e n p e r f o r m e d on a r a t h e r l a r g e s c a l e . M e a s u r i n g of t h e l o n g r e f r a c t i o n p r o f i l e s h a s b e e n m a d e p o s s i b l e by c l o s e c o o p e r a t i o n b e t w e e n t h e v a r i o u s c o u n t r i e s . In all t h e S c a n d i n a v i a n c o u n t r i e s it w a s m o r e o r l e s s at r a n d o m w h a t i n s t i t u t i o n s took c h a r g e of s e i s m o l o g y f r o m t h e v e r y b e g i n n i n g . T h e s c i e n t i s t who f i r s t r e a l i z e d t h e i m p o r t a n c e of t h i s n e w s c i e n c e h a d to i n c o r p o r a t e it in t h e b r a n c h of k n o w l e d g e he d i r e c t e d , a n d to l e t h i s c o l l a b o r a t o r s m a n a g e t h e p r a c t i c a l work. T h a t i s t h e r e a s o n w h y t h e s e i s m i c s e r v i c e in D e n m a r k i s
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r u n by the Geodetic I n s t i t u t e , in I c e l a n d by the W e a t h e r B u r e a u , but in the o t h e r c o u n t r i e s by the u n i v e r s i t i e s ( B e r g e n , Uppsala, and Helsinki). E v e n within the u n i v e r s i t i e s t h e r e a r e d i f f e r e n c e s a s to the o r g a n i z a t i o n . In B e r g e n , the s e i s m o l o g i c a l s e r v i c e is p a r t of the geological d e p a r t m e n t . In U p p s a l a it began a s a p a r t of the m e t e o r o l o g i c a l d e p a r t m e n t , but i s now an i n d e p e n dent i n s t i t u t e . In Helsinki, h o w e v e r , the " f a t h e r " of s e i s m o l o g y is p u r e p h y s i c s . T h i s m e a n s that when Scandinavian s e i s m o l o g i s t s m e e t e a c h other, they b r i n g d i f f e r e n t e d u c a tional b a c k g r o u n d s with t h e m ; g e o d e s i s t s , g e o l o g i s t s , m e t e o r o l o g i s t s , p h y s i c i s t s . T h e i r s o c i e t y h a s in r e c e n t y e a r s been joined by e l e c t r o n i c e n g i n e e r s and c o m p u t e r s p e c i a l i s t s . S e i s m o l o g y h a s had the fate that a f t e r having been a p u r e s c i e n c e for two g e n e r a t i o n s , politic i a n s h a v e now d i s c o v e r e d that s e i s m o g r a p h s t a t i o n s of v e r y high s e n s i t i v i t y might be u s e d for d e t e c t i n g u n d e r g r o u n d n u c l e a r e x p l o s i o n s . T h e r e f o r e , d u r i n g the l a s t few y e a r s i n s t i t u t i o n s o t h e r t h a n the r e s e a r c h i n s t i t u t i o n s m e n t i o n e d above have e n t e r e d the p i c t u r e , a s f o r i n s t a n c e the D e f e n c e R e s e a r c h C o u n c i l s of Norway and of Sweden. T h e r e is no doubt that the viewpoints and e x p e r i e n c e s brought into s e i s m o l o g y in t h i s way will be of value and that cooperation between s c i e n t i s t s and t e c h n i c i a n s in the f u t u r e will p r o v e to be fruitful in Scandinavia as it h a s a p p e a r e d to be in. f o r i n s t a n c e , . t h e U.S.A.
Education in seismology in Scandinavia Up to a v e r y few y e a r s ago, all Scandinavian s e i s m o l o g i s t s w e r e s e l f - t a u g h t a s to t h i s topic. T h i s fact did not in a n y w a y p r e s e n t o u t s t a n d i n g c o n t r i b u t i o n s to the s c i e n c e . M i s s I . L e h m a n n one of the p i o n e e r s within s e i s m o l o g y who i s still going s t r o n g - w a s the chief of the S e i s m o l ogical S e r v i c e in Copenhagen f r o m 1928 to 1953. In Uppsaia, an i n t e r n a t i o n a l r e s e a r c h c e n t r e of w i d e s p r e a d r e p u t a t i o n h a s b e e n s e t up. I m p o r t a n t c o n t r i b u t i o n s to the s c i e n c e of s e i s m o l o g y a l s o have been r e l e a s e d f r o m the o t h e r i n s t i t u t i o n s . N e v e r t h e l e s s , t h e r e i s a g r o w i n g f e e l i n g that while all s c i e n c e - including s e i s m o l o g y - i s going to b e c o m e m o r e and m o r e s p e c i a l i z e d , and while at the s a m e t i m e m o r e and m o r e young s c i e n t i s t s a r e needed, s e i s m o l o g y and r e l a t e d s u b j e c t s will have to be taught r e g u l a r l y at the u n i v e r s i t i e s . At s o m e of the Scandinavian u n i v e r s i t i e s ( B e r g e n , Copenhagen, Helsinki, Uppsaia) r e g u l a r l e c t u r e s on s e i s m o l o g y a r e now given, and s t u d e n t s can take t h e i r final d e g r e e not only in b r o a d e r f i e l d s s u c h a s geology, p h y s i c s o r g e o p h y s i c s but a l s o in the s p e c i f i c field topic of seismology. H. JENSEN
Mining Research in Sweden
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The Iron M o n g e r s ' B u r e a u of M i n e s w a s founded in 1936 a s a f o r u m f o r s u b j e c t s of c o m m o n i n t e r e s t for the m i n i n g i n d u s t r y . In 1941, the Swedish Mining A s s o c i a t i o n w a s founded and joined the F e d e r a t i o n of S w e d i s h I n d u s t r i e s . P r a c t i c a l l y all the m i n i n g c o m p a n i e s of Sweden a r e m e m b e r s of the Mining A s s o c i a t i o n . At the t u r n of the y e a r 1949-1950, the I r o n M o n g e r s ' B u r e a u of M i n e s w a s i n c o r p o r a t e d in the Swedish Mining A s s o c i a t i o n . Mining r e s e a r c h i s an activity within the Mining A s s o c i a t i o n . A head c o m m i t t e e with a m a x i m u m of ten m e m b e r s i s in c h a r g e of the r e s e a r c h . The m a n a g i n g d i r e c t o r of the Mining A s s o c i a t i o n i s c h a i r m a n of the c o m m i t t e e . At p r e s e n t t h r e e of the p r o f e s s o r s at the m i n i n g division of the Royal I n s t i t u t e of T e c h n o l o g y a r e m e m b e r s of t h i s c o m m i t t e e . The o t h e r m e m b e r s r e p r e s e n t the m i n i n g i n d u s t r y . The p r o f e s s o r s a r e g e n e r a l l y r e - e l e c t e d when the m a n d a t e e x p i r e s . T h i s g i v e s a good connection to r e s e a r c h and i n s t r u c t i o n at the Royal I n s t i t u t e of T e c h n o l o g y and a good contact with r e p r . e s e n t a t i v e s f r o m i n d u s t r y . T h e a c t i v i t i e s of the "Mining R e s e a r c h " group a r e divided into five s u b j e c t s : (1) Geology with g e o p h y s i c s and g e o c h e m i s t r y . (2) Rock b r e a k i n g and excavation. (3) Mining m a c h i n e r y . (4) M i n e r a l d r e s s i n g . (5) W o r k e r s ' w e l f a r e and hygiene. E a c h s u b j e c t i s s u p e r v i s e d by a c o m m i t t e e of t h r e e m e m b e r s who have to: (a) d i s c u s s p r o p o s e d r e s e a r c h p r o j e c t s and b r i n g f o r w a r d r e c o m m e n d e d s u b j e c t s to the head c o m m i t t e e ; (b) m a k e p r o g r a m m e s and c a l c u l a t e c o s t s f o r the r e a l i z a t i o n of r e c o m m e n d e d p r o j e c t s ; (c) p r o p o s e m e m b e r s to the working c o m m i t t e e s ; (d) r e p o r t twice a y e a r a s u m m a r y of t h e c o m m i t t e e s within the s u b j e c t s group. E a c h p r o f e s s o r of t h e m i n i n g d i v i s i o n s i s g e n e r a l l y c h a i r m a n of h i s s u b j e c t g r o u p and a l s o of s o m e working c o m m i t t e e s .
Solid-Earth Geophysics in Scandinavia GEOMAGNETISM IN SCANDINAVIA Only a b r i e f outline of s o m e of the p r a c t i c a l a s p e c t s of g e o m a g n e t i s m in Scandinavia can be given h e r e . R e s e a r c h work is p u r s u e d at s o m e of the m a g n e t i c o b s e r v a t o r i e s m e n t i o n e d below and by s c a t t e r e d g r o u p s , e.g., at the U n i v e r s i t y of B e r g e n , Norwegian I n s t i t u t e of C o s m i c P h y s i c s , Royal Swedish I n s t i t u t e of Technology and the K i r u n a Geophysical O b s e r v a t o r y . The p r i n c i p a l f i e l d s of i n v e s t i g a t i o n p e r t a i n to a r c h a e o - and p a l a e o m a g n e t i s m , c r u s t conductivity, r a p i d v a r i a t i o n s , a u r o r a l p h e n o m e n a , u p p e r a t m o s p h e r e and m a g n e t o s p h e r e . I n t e r - N o r d i c cooperation in g e o m a g n e t i s m h a s always been noteworthy. Two of the m o s t n o table e x a m p l e s a r e : (1) T h e C h a r t s of A v e r a g e G e o m a g n e t i c E l e m e n t s D, H and Z 1955.0 for D e n m a r k , Finland, Norway, Sweden, which w e r e p u b l i s h e d jointly by the four c o u n t r i e s ; (2) The p a r t i c i p a t i o n in the a e r o m a g n e t i c s u r v e y of Scandinavia p e r f o r m e d in the a u t u m n of 1965 by the Dominion O b s e r v a t o r y , Ottawa, with 35 k m line spacing. Dennzark
The g e o m a g n e t i c work is s u p e r v i s e d by the D a n i s h M e t e o r o l o g i c a l Institute. O b s e r v a t o r i e s . R e g u l a r o b s e r v a t i o n s began at the Copenhagen O b s e r v a t o r y in 1891. It w a s r e placed by Rude Skov in 1906. Rude Skov h a s , for m a n y y e a r s , been a s t a n d a r d o b s e r v a t o r y f r o m which the o b s e r v a t o r i e s in the o t h e r Nordic c o u n t r i e s have o b t a i n e d t h e i r a b s o l u t e field values. Since the d e v e l o p m e n t of the c e l e b r a t e d La Cour s y s t e m of r e c o r d i n g and " s e m i - a b s o l u t e " m a g netic i n s t r u m e n t s , D e n m a r k h a s e x p o r t e d - on a s t r i c t n o n - p r o f i t b a s i s - m a g n e t i c i n s t r u m e n t s a r o u n d the world. Rude Skov is the b a s i s of all m a g n e t i c work in Greenland. Absolute s t a n d a r d : c l a s s i c a l i n s t r u m e n t s and proton m a g n e t o m e t e r . Godhavn, G r e e n l a n d , s t a r t e d in 1926, Thule, G r e e n l a n d , h a s occupied its p r e s e n t s i t e s i n c e 1955. All o b s e r v a t o r i e s have n o r m a l m a g n e t o g r a p h s and La Cour quickrun. S u r v e y s . A g e n e r a l m a g n e t i c s u r v e y was m a d e between 1890 and 1905. Since then s p o r a d i c s u r v e y s have been m a d e of s e l e c t e d a r e a s . A net of about ten s e c u l a r s t a t i o n s is r e o c c u p i e d e v e r y five y e a r s . In the s u m m e r of 1965, a s u r v e y was m a d e of the west c o a s t of Greenland. About 50 s t a t i o n s w e r e m e a s u r e d between l a t i t u d e s of 61°N and 75°N. F i~l la nd O b s e r v a t o r i e s . At Nurmij~irvi, u n d e r the s u p e r v i s i o n of the F i n n i s h M e t e o r o l o g i c a l Office, o b s e r v a t i o n s Started in 1953 u s i n g the n o r m a l r e c o r d e r , La Cour q u i c k r u n and e a r t h c u r r e n t s for one component ( r e s o l u t i o n 1 sec). Absolute s t a n d a r d is b a s e d on the proton m a g n e t o m e t e r and Nordic c o m p a r i s o n s . Sodankyl~i is s u p e r v i s e d by the F i n n i s h A c a d e m y of Science. It o p e r a t e d f r o m 1914 to 1944. A f t e r i n t e r r u p t i o n due to w a r d e s t r u c t i o n , r e g u l a r r e c o r d i n g s t a r t e d again in 1946 u s i n g the n o r m a l r e c o r d e r , La Cour q u i c k r u n , e a r t h c u r r e n t s and the G5ttingen pulsation r e c o r d e r . Absolute v a l u e s a r e obtained t h r o u g h c o m p a r i s o n s .
AI09
Surveys. A g e n e r a l magnetic ground survey f r o m about 1,000 stations was made in 1910-1928. About 40 s e c u l a r stations have been reoccupied at r e g u l a r i n t e r v a l s (since 1950, almost yearly). Supervision: the Finnish Meteorological Office. About 80~ of Finland has been c o v e r e d by a lowaltitude (150 m) a e r o m a g n e t i c survey of the totaI intensity, with line spacin~ of 400 m ( s u p e r vision: the Geological Survey of Finland). Norway Observatories. Domb~ls is p r e s e n t l y under the supervision of the Geophysical Institute of the University of Bergen. O b s e r v a t i o n s began in 1916. Absolute values have been ,riven s i n c e 1952 when the new site was occupied. The n o r m a l r e c o r d e r is used. Absolute s t a n d a r d is d e r i v e d through Nordic c o m p a r i s o n s . T r o m s 5 (the Norwegian Institute of Cosmic P h y s i c s ) s t a r t e d in 1930 using the n o r m a l r e c o r d e r and the G6ttingen pulsation r e c o r d e r . Absolute values are d e r i v e d through c o m p a r i s o n s . The staff of T r o m s 5 also o p e r a t e s the magnetic station on Bear Island. Surveys. Through the joint effort of the Hydrographic Office of Norway and the Magnetic Bureau in Bergen, a net of 120 s e c u l a r stations was m e a s u r e d and reduced to epoch 1941.5. Another net of about 1,000 stations was reduced to 1947.5. In addition, the Hydrographic Office has issued four m a p s of declination covering s o m e coastal w a t e r s of outstanding anomalies. The Geographical Survey of Norway also c a r r i e d out a large n u m b e r of magnetic o b s e r v a t i o n s in 1941-1957. In 1965, the whoIe survey work in Norway was taken over by the Geographical S u r vey Office. S c a t t e r e d o b s e r v a t i o n s along the coast of Svalbard have been made by the Norwegian Polar Institute (Norsk P o l a r Institute) as well as by Swedish and other foreign expeditions. Sweden Observatories. At Lov5 (the Swedish Board of Shipping and Navigation) o b s e r v a t i o n s began in 1927. Normal r e c o r d e r s and L a Cour quickrun are used. Absolute standard: proton m a g n e t o m e t e r and Nordic c o m p a r i s o n s . An auxiliary station, EnkSping, operating a Gbttingen pulsation r e c o r d e r , began r e c o r d i n g in 1963. Abisko (under joint s u p e r v i s i o n of the Board of Shipping and the Royal S w e d i s h / ~ c a d e m y of Sciences) has been recording, with i n t e r r u p t i o n s , since 1921 using n o r m a l r e c o r d e r s and part of the t i m e , La Cour quickrun. Absolute s t a n d a r d is reached by c o m p a r i s o n s . Kiruna (the Royal Swedish Academy of Sciences) began magnetic r e c o r d i n g about 1950, mostly as a complement to other e x p e r i m e n t s at the Geophysical O b s e r v a t o r y . P r e s e n t equipment includes normal r e c o r d e r s , GSttingen pulsation r e c o r d e r , Bould.er type r e cording in audio and subandio frequency range, e a r t h c u r r e n t s . An automatic s y s t e m of obtaining magnetic data in digital form has o p e r a t e d since 1965. Absolute values are obtained through c o m p a r i s o n s . Surveys. A number of o b s e r v a t i o n s along the coasts of Sweden and in surrounding w a t e r s have been p e r f o r m e d since about 1913. The s h i p - b o r n e s u r v e y s have largely been a joint effort by Sweden and Finland. A g e n e r a l survey (about 2,100 stations) was made in 1928-1934 by the Swedish Geological Survey. One net of about one hundred s e c u l a r stations e x i s t s since 1928 and another, of ten stations, since 1953 (the Swedish Board of Shipping and Navigation). Availability of geomagnetic data f o r Scandinavia Yearbooks giving monthlytabulations of mean hourly values in t h r e e components, annual mean values, C and K indices, etc., a r e i s s u e d r e g u l a r l y for the following o b s e r v a t o r i e s : Rude Skov, Godhavn, Thule, Nurmij~irvi, Sodankyl~i, DomNts, T r o m s S , LovS, Abisko, and Kiruna. Information r e g a r d i n g yearbooks, other publications, and magnetic c h a r t s can be obtained through the Swedish Board of Shipping and Navigation, Geomagnetic Section, Stockholm 27, Sweden. F. E L E M A N
GRAVIMETRY IN SCANDINAVIA
Gravirnetric observations on land
AIIO
T h e r e is a tradition of g r a v i m e t r i c work in Scandinavia. S e r i e s of pendulum o b s e r v a t i o n s w e r e undertaken in all the Scandinavian countries at the end of the last century and the i n v e s tigations continued until the t h i r t i e s of this century. A special survey was c a r r i e d out by the
Baltic Geodetic C o m m i s s i o n : studies of the pendulum m e a s u r e m e n t s , t h e i r c o r r e c t i o n s , and o t h e r f a c t o r s influencing the o b s e r v a t i o n s w e r e p e r f o r m e d at s e v e r a l places. It may also be mentioned that an investigation of the g r a v i m e t r i c t i e s between Copenhagen, the o t h e r Scandinavian capitals and a s e r i e s of European pendulum base stations was c a r r i e d out by N~rlund in the middle of the n i n e t e e n - t h i r t i e s . Scandinavia has also contributed to the development of m o d e r n g r a v i m e t e r s . At the beginning of this century, Ising c o n s t r u c t e d his f i r s t g r a v i m e t e r . It is only r e g r e t t a b l e that other work p r e v e n t e d Ising f r o m spending m o r e t i m e on this project. L a t e r on, g r a v i m e t e r s w e r e cons t r u c t e d by Lindblad and G. Malmqvist (the Boliden G r a v i m e t e r ) , and by Ndrgaard. The l a t t e r contributed a s e r i e s of different types which have been in use in s e v e r a l c o u n t r i e s a l l o v e r the world until recent y e a r s . Denmark
Due to the easy topography in Denmark, it has been a relatively easy task to produce topogra@hic m a p s ot the scale 1:20,000. T h e r e f o r e , it is not s u r p r i s i n g that the g r a v i m e t r i c net is v e r y dense: the distance between the g r a v i m e t r i c stations is not m o r e than 1.5 km and in many c a s e s l e s s than 1 kin. M e a s u r e m e n t s have been c a r r i e d out all over Denmark, including the s m a l l islands. Most of the r e s u l t s have been published by the Danish Geodetic Institute (Dansk Geoteknisk Institut), which has been r e s p o n s i b l e for the g r a v i m e t r i c work. The re/naining p o r tion of the o b s e r v a t i o n s is in the p r o c e s s of being published. In r e c e n t y e a r s , Aarhus U n i v e r s i t y has taken up detailed g r a v i m e t r i c studies in .connection with g e o p h y s i c a l - g e o l o g i c a l p r o b l e m s , e.g., t e c t o n i c s of salt domes, geological s t r u c t u r e s . In the F a r o e s , the f i r s t g r a v i m e t r i c s u r v e y was p e r f o r m e d by the Geodetic Institute in 1959 and another m o r e detailed s u r v e y was executed tn 1964. The Geodetic Institute has also u n d e r taken g r a v i m e t r i c m e a s u r e m e n t s in Greenland since 1950. Most of the r e s u l t s have been published. Finland
Finland was the f i r s t of the Scandinavian countries to publish a complete g r a v i m e t r i c map. The net is dense and the stations a r e equally d i s t r i b u t e d o v e r the country. However, the m o s t important contribution to gravity f r o m Finland is the work c a r r i e d out at the I s o s t a t i c Institute. Since the e s t a b l i s h m e n t 6f the institute (in 1938) up to now, 50 publications have been made. It also d e s e r v e s mention that the founder and d i r e c t o r of the institute, W.W. Heiskanen, b e s i d e s being d i r e c t o r of the Finnish Geodetic Institute, has been the leading p e r s o n in the e s t a b l i s h m e n t of the Ohio State University Institute for Geodesy, P h o t o g r a m m e t r y , and Cartography, f r o m which many valuable g r a v i m e t r i c p a p e r s have been published in r e c e n t years. Another contribution to g r a v i m e t r i c r e s e a r c h f r o m Finland is the relationship between gravity and the uplift of Scandinavia. Norway and Sweden
G r a v i m e t r i c field work in Norway andSweden is m o r e difficult due to the difficult topography. G r a v i m e t r i c m a p s of t h e s e c o u n t r i e s exist, but the spacing b e t w e e n t h e stations is very variable, e s p e c i a l l y in Norway, w h e r e stations in the mountain a r e a s a r e very s p a r s e . The m e a s u r e m e n t s r e p o r t e d f r o m Finland, Norway, and Sweden have been c a r r i e d out by the Geodetic Institutes and the Geographical Survey of Norway and the Geographical Survey Office of Sweden, r e s p e c t i v e l y . B e s i d e s , a s e r i e s of very detailed m e a s u r e m e n t s a r e being c a r r i e d out by p r o s p e c t i n g companies and g o v e r n m e n t a l agencies such as the Geological Surveys o r the u n i v e r s i t i e s . T h e s e s u r v e y s are tied into the geodetic s y s t e m s . Iceland
In Iceland, t h e D a n i s h G e o d e t i c Institute p e r f o r m e d a s e r i e s of pendulum o b s e r v a t i o n s in 1900. In the n i n e t e e n - t h i r t i e s , a G e r m a n expedition e s t a b l i s h e d a few pendulum s t a t i o n s while a detailed s u r v e y by m e a n s of g r a v i m e t e r s was undertaken by E i n a r s o n in 1950-1954. The r e s u l t s which w e r e published in 1954 have contributed to the geophysical-geologicai h i s t o r y of Iceland. G r a v i t y o b s e r v a t i o n s at s e a
So f a r only g r a v i m e t r i c o b s e r v a t i o n s of land a r e a s have been mentioned. However, Scandinavia has been active in s e a - g r a v i t y r e s e a r c h also. Of the t h r e e existing Vening Meinesz pendulums, one set belongs to the Danish Geodetic Institute. M e a s u r e m e n t s by m e a n s of this i n s t r u m e n t have been p e r f o r m e d by the Norwegian Geodetic Institute along the Norwegian Atlantic coast. The in-
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TECTONOPHYSICS International Journal of Geotectonics and the Geology and Physics of the Interior of the Earth SPECIAL ISS~JE ON EUROPEAN EARTHQUAKE MECHANISMS Edited by A.R. R i t s e m a
E d i t o r i a l - Earthquake m e c h a n i s m s : a European survey CA.R. Ritsema, De Bilt, The Netherlands) P o s s i b i l i t e s of determination of values of s t r e s s acting in earthquake foci (A.V. Vvedenskaya, Moscow, U.S.S.R.) On plastic deformations within the earthquake focus (K.V. Pshennikov, Irkutsk, U.S.S.R.) Computer work and mechanism studies (R.E. Ibgram, S.J., Dublin, Ireland) The focal mechanism of earthquakes in the southern coast of the Iberian Peninsula CA. Udias, S.J., Frankfort/Main, Germany) Computer determinations for the fault-plane solutions in and near Anatolia (N. Canitez and S. Balamir Tjcer, Istanbul, Turkey) On the use of surface waves in earthquake mechanism studies Cabstract) (A. Beu-Menahem, Rehovoth, Israel) Mechanisms of European earthquakes CA.R. Ritsema, De Bilt, The Netherlands) Rezente vertikale Erdkrustenbewegungen in Europa (L. Hiersemann, Halle/Saale, Germany) Synthetic seismic pulses from propagating faults (abstract) (B. Berekhemer and K.H. Jacob, Frankfort/Main, Germany) Fault-plane solutions of earthquakes in Baden-Wiirtemberg (abstract) (G. Schneider, R. Schick and H. Berekhemer, Stuttgart, Germany) Bibliography of recent crustal movements in Europe (L. Hiersemann, Halle/Saale, Germany)
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s t r u m e n t h a s a l s o b e e n emlSloyed in Sweden. T h e F i n n s h a v e c a r r i e d out m e a s u r e m e n t s in t h e B a l t i c S e a a n d in t h e A r c t i c S e a by m e a n s of a b o t t o m g r a v i m e t e r , w h i l e U p p s a l a U n i v e r s i t y , S w e d e n , in a s i m i l a r way, h a s s t u d i e d a s p e c i a l r e g i o n in t h e B a l t i c Sea. R e c e n t l y , t h e D a n i s h G e o d e t i c I n s t i t u t e p u r c h a s e d an A s k a n i a s u r f a c e - s h i p g r a v i m e t e r a n d e x e c u t e d m e a s u r e m e n t s in t h e D a n i s h w a t e r s a s w e l l a s in t h e G r e e n l a n d Sea. In c o n c l u s i o n , it m u s t be s t a t e d t h a t e v e n if m o r e d e t a i l e d g r a v i m e t r i c s t u d i e s a r e n e e d e d , S c a n d i n a v i a , o r r a t h e r t h e N o r d i c c o u n t r i e s , a r e r e l a t i v e l y w e l l s u p p l i e d w i t h g r a v i m e t r i c data. S. SAXOV
S E I S M O L O G Y IN SCANDINAVIA
History of Seismology in Scandinavia W h e n , in 1899, r e c o r d i n g of t e l e s e i s m i c e v e n t s w a s f o u n d to be p o s s i b l e , a r i c h s c i e n t i f i c and t e c h n i c a l d e v e l o p m e n t b e g a n all o v e r t h e w o r l d w h i c h r e v e a l e d u n e x p e c t e d f a c t s about e a r t h q u a k e s a n d t h e e a r t h ' s i n t e r i o r . In s c i e n c e , o b s e r v a t i o n s a r e b e t t e r t h a n s p e c u l a t i o n s a s f o u n d a t i o n s f o r r e s u l t s , a n d in t h e e a s e of s e i s m o l o g y , o b s e r v a t i o n s m e a n e s t a b l i s h m e n t of s e i s m o graph stations. In S c a n d i n a v i a , t h e f i r s t s t a t i o n s w e r e e s t a b l i s h e d in 1904. In t h i s y e a r a o n e - c o m p o n e n t B o s c h s e i s m o g r a p h w a s put into o p e r a t i o n in B e r g e n ( N o r w a y ) a n d a t w o - c o m p o n e n t W i e c h e r t . H o r i z o n t a l in U p p s a l a (Sweden). Soon a f t e r , two m o r e s t a t i o n s followed: R e y k j a v i k ( I c e l a n d ) in 1909 a n d D i s c o I s l a n d ( G r e e n l a n d , o p e r a t e d f r o m D e n m a r k ) in 1910. T h e F i r s t W o r l d W a r r e t a r d e d f u r t h e r d e v e l o p m e n t , but in t h e y e a r s a f t e r t h e w a r , w o r k w a s t a k e n up a g a i n : H e l s i n k i ( F i n l a n d ) s t a r t e d o p e r a t i n g in 1924, C o p e n h a g e n ( D e n m a r k ) in 1927, a n d t h e G r e e n l a n d s t a t i o n s S c o r e s b y s u n d and I v i g t u t in 1928 and 1929. T h e D i s c o I s l a n d s t a t i o n w a s c l o s e d down a l t e r a few y,~ars and t h e I v i g t u t s t a t i o n in 1960; all t h e r e m a i n i n g s t a t i o n s a r e s t i l l o p e r a t i n g . T h e d e v e l o p m e n t of s e i s m o l o g y c o v e r s a wide field: f r o m t h e s i m p l e h o r i z o n t a l p e n d u l u m o v e r t h e W i e c h e r t s o r M a i n k a s ( s o m e of w h i c h a r e o p e r a t i n g t o d a y ) to t h e m o r e s o p h i s t i c a t e d e l e c t r o m a g n e t i c i n s t r u m e n t s of t h e G a l i t z i n type. In a p e r i o d c o v e r i n g a few y e a r s b e f o r e to s o m e y e a r s a f t e r t h e S e c o n d W o r l d W a r , m o s t of t h e s t a t i o n s w e r e e q u i p p e d w i t h s h o r t - p e r i o d v e r t i c a l s , t h e s e s e i s m o g r a p h s h a v i n g p r o v e d to be so v e r y u s e f u l f o r p r e c i s e r e a d i n g of P - w a v e s . At t h e s a m e t i m e , m a n y m o r e s t a t i o n s w e r e e s t a b l i s h e d . In s o m e of t h e m t h e e q u i p m e n t w a s r a t h e r s p a r s e , in o t h e r s m o r e a d v a n c e d , but m o s t of t h e m w e r e r u n n i n g an S P Z - i n s t r u m e n t . T h e n e x t w a v e of " r e - e q u i p m e n t " s e t in w h e n t h e W o r l d - W i d e S e i s m o g r a p h S y s t e m N e t w o r k w a s e s t a b l i s h e d by t h e U.S. C o a s t and G e o d e t i c S u r v e y d u r i n g t h e y e a r s 1961-1963. At t h e p r e s e n t t i m e , s t a n d a r d i n s t r u m e n t s of t h i s t y p e a r e in o p e r a t i o n at t h r e e G r e e n l a n d i c s t a t i o n s a n d at f i v e s t a t i o n s in S c a n d i n a v i a , p a r t l y at old s t a t i o n s t o g e t h e r with t h e p r e v i o u s i n s t r u m e n t a t i o n , p a r t l y at s t a t i o n s e s t a b l i s h e d ad hoc. O n e of t h e n e w e s t a d v a n c e s w i t h i n i n s t r u m e n t a l s e i s m o l o g y i s t h e u s e of s e i s m o g r a p h s a r r a y s . H o w e v e r , e v e n a s m a l l s i z e a r r a y i s a r a t h e r e x p e n s i v e i n s t r u m e n t to r u n . T h e r e f o r e , i n t e r N o r d i c d i s c u s s i o n s h a v e t a k e n p l a c e in o r d e r to d i s c o v e r how t h e f o r c e s m a y be j o i n e d in t h e b e s t m a n n e r . At t h r e e o r f o u r l o c a l i t i e s within S c a n d i n a v i a ( i n c l u d i n g G r e e n l a n d ) e x p e r i m e n t a l array stations have been established.
Seismology today T o d a y t h e N o r d i c c o u n t r i e s a r e r u n n i n g a b o u t 25 s e i s m o g r a p h s t a t i o n s . T h i s d e n s e n e t w o r k m e a n s t h a t S c a n d i n a v i a h a s a c o v e r i n g w e l l up to an i n t e r n a t i o n a l s t a n d a r d , a s f a r a s t e l e s e i s m i c r e c o r d i n g i s c o n c e r n e d . H o w e v e r , e v e n if t h e s e i s m i c i t y in all t h e c o u n t r i e s in q u e s t i o n i s s m a l l , m i n o r e v e n t s m a y o c c u r . In I c e l a n d , s u c h e v e n t s a r e v e r y f r e q u e n t . T h e A r c t i c r e g i o n s a l s o a p p e a r to be t h e s i t e of m a n y s m a l l e a r t h q u a k e s . E v e n in t h e a r e a s w i t h a m i n i m u m of s e i s m i c i t y D e n m a r k a n d s o m e p a r t s of F i n l a n d a n d N o r w a y - e a r t h q u a k e s a r e not e n t i r e l y a b s e n t . T h e s e s m a l l e v e n t s m a y be of g r e a t i n t e r e s t f r o m a s c i e n t i f i c p o i n t of view, but it i s d i f f i c u l t to s u b j e c t t h e m to a c o m p r e h e n s i v e s t u d y by m e a n s of t h e e x i s t i n g n e t of s t a t i o n s . T h e r e f o r e , all t h e c o u n t r i e s in q u e s t i o n a r e w o r k i n g f o r t h e e s t a b l i s h m e n t of a d e n s e r n e t of l o c a l s t a t i o n s . It s h o u l d a l s o be m e n t i o n e d t h a t i n v e s t i g a t i o n s on t h e s t r u c t u r e of t h e c r u s t a n d u p p e r m a n t l e h a v e b e e n p e r f o r m e d on a r a t h e r l a r g e s c a l e . M e a s u r i n g of t h e l o n g r e f r a c t i o n p r o f i l e s h a s b e e n m a d e p o s s i b l e by c l o s e c o o p e r a t i o n b e t w e e n t h e v a r i o u s c o u n t r i e s . In all t h e S c a n d i n a v i a n c o u n t r i e s it w a s m o r e o r l e s s at r a n d o m w h a t i n s t i t u t i o n s took c h a r g e of s e i s m o l o g y f r o m t h e v e r y b e g i n n i n g . T h e s c i e n t i s t who f i r s t r e a l i z e d t h e i m p o r t a n c e of t h i s n e w s c i e n c e h a d to i n c o r p o r a t e it in t h e b r a n c h of k n o w l e d g e he d i r e c t e d , a n d to l e t h i s c o l l a b o r a t o r s m a n a g e t h e p r a c t i c a l work. T h a t i s t h e r e a s o n w h y t h e s e i s m i c s e r v i c e in D e n m a r k i s
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r u n by the Geodetic I n s t i t u t e , in I c e l a n d by the W e a t h e r B u r e a u , but in the o t h e r c o u n t r i e s by the u n i v e r s i t i e s ( B e r g e n , Uppsala, and Helsinki). E v e n within the u n i v e r s i t i e s t h e r e a r e d i f f e r e n c e s a s to the o r g a n i z a t i o n . In B e r g e n , the s e i s m o l o g i c a l s e r v i c e is p a r t of the geological d e p a r t m e n t . In U p p s a l a it began a s a p a r t of the m e t e o r o l o g i c a l d e p a r t m e n t , but i s now an i n d e p e n dent i n s t i t u t e . In Helsinki, h o w e v e r , the " f a t h e r " of s e i s m o l o g y is p u r e p h y s i c s . T h i s m e a n s that when Scandinavian s e i s m o l o g i s t s m e e t e a c h other, they b r i n g d i f f e r e n t e d u c a tional b a c k g r o u n d s with t h e m ; g e o d e s i s t s , g e o l o g i s t s , m e t e o r o l o g i s t s , p h y s i c i s t s . T h e i r s o c i e t y h a s in r e c e n t y e a r s been joined by e l e c t r o n i c e n g i n e e r s and c o m p u t e r s p e c i a l i s t s . S e i s m o l o g y h a s had the fate that a f t e r having been a p u r e s c i e n c e for two g e n e r a t i o n s , politic i a n s h a v e now d i s c o v e r e d that s e i s m o g r a p h s t a t i o n s of v e r y high s e n s i t i v i t y might be u s e d for d e t e c t i n g u n d e r g r o u n d n u c l e a r e x p l o s i o n s . T h e r e f o r e , d u r i n g the l a s t few y e a r s i n s t i t u t i o n s o t h e r t h a n the r e s e a r c h i n s t i t u t i o n s m e n t i o n e d above have e n t e r e d the p i c t u r e , a s f o r i n s t a n c e the D e f e n c e R e s e a r c h C o u n c i l s of Norway and of Sweden. T h e r e is no doubt that the viewpoints and e x p e r i e n c e s brought into s e i s m o l o g y in t h i s way will be of value and that cooperation between s c i e n t i s t s and t e c h n i c i a n s in the f u t u r e will p r o v e to be fruitful in Scandinavia as it h a s a p p e a r e d to be in. f o r i n s t a n c e , . t h e U.S.A.
Education in seismology in Scandinavia Up to a v e r y few y e a r s ago, all Scandinavian s e i s m o l o g i s t s w e r e s e l f - t a u g h t a s to t h i s topic. T h i s fact did not in a n y w a y p r e s e n t o u t s t a n d i n g c o n t r i b u t i o n s to the s c i e n c e . M i s s I . L e h m a n n one of the p i o n e e r s within s e i s m o l o g y who i s still going s t r o n g - w a s the chief of the S e i s m o l ogical S e r v i c e in Copenhagen f r o m 1928 to 1953. In Uppsaia, an i n t e r n a t i o n a l r e s e a r c h c e n t r e of w i d e s p r e a d r e p u t a t i o n h a s b e e n s e t up. I m p o r t a n t c o n t r i b u t i o n s to the s c i e n c e of s e i s m o l o g y a l s o have been r e l e a s e d f r o m the o t h e r i n s t i t u t i o n s . N e v e r t h e l e s s , t h e r e i s a g r o w i n g f e e l i n g that while all s c i e n c e - including s e i s m o l o g y - i s going to b e c o m e m o r e and m o r e s p e c i a l i z e d , and while at the s a m e t i m e m o r e and m o r e young s c i e n t i s t s a r e needed, s e i s m o l o g y and r e l a t e d s u b j e c t s will have to be taught r e g u l a r l y at the u n i v e r s i t i e s . At s o m e of the Scandinavian u n i v e r s i t i e s ( B e r g e n , Copenhagen, Helsinki, Uppsaia) r e g u l a r l e c t u r e s on s e i s m o l o g y a r e now given, and s t u d e n t s can take t h e i r final d e g r e e not only in b r o a d e r f i e l d s s u c h a s geology, p h y s i c s o r g e o p h y s i c s but a l s o in the s p e c i f i c field topic of seismology. H. JENSEN
Mining Research in Sweden
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The Iron M o n g e r s ' B u r e a u of M i n e s w a s founded in 1936 a s a f o r u m f o r s u b j e c t s of c o m m o n i n t e r e s t for the m i n i n g i n d u s t r y . In 1941, the Swedish Mining A s s o c i a t i o n w a s founded and joined the F e d e r a t i o n of S w e d i s h I n d u s t r i e s . P r a c t i c a l l y all the m i n i n g c o m p a n i e s of Sweden a r e m e m b e r s of the Mining A s s o c i a t i o n . At the t u r n of the y e a r 1949-1950, the I r o n M o n g e r s ' B u r e a u of M i n e s w a s i n c o r p o r a t e d in the Swedish Mining A s s o c i a t i o n . Mining r e s e a r c h i s an activity within the Mining A s s o c i a t i o n . A head c o m m i t t e e with a m a x i m u m of ten m e m b e r s i s in c h a r g e of the r e s e a r c h . The m a n a g i n g d i r e c t o r of the Mining A s s o c i a t i o n i s c h a i r m a n of the c o m m i t t e e . At p r e s e n t t h r e e of the p r o f e s s o r s at the m i n i n g division of the Royal I n s t i t u t e of T e c h n o l o g y a r e m e m b e r s of t h i s c o m m i t t e e . The o t h e r m e m b e r s r e p r e s e n t the m i n i n g i n d u s t r y . The p r o f e s s o r s a r e g e n e r a l l y r e - e l e c t e d when the m a n d a t e e x p i r e s . T h i s g i v e s a good connection to r e s e a r c h and i n s t r u c t i o n at the Royal I n s t i t u t e of T e c h n o l o g y and a good contact with r e p r . e s e n t a t i v e s f r o m i n d u s t r y . T h e a c t i v i t i e s of the "Mining R e s e a r c h " group a r e divided into five s u b j e c t s : (1) Geology with g e o p h y s i c s and g e o c h e m i s t r y . (2) Rock b r e a k i n g and excavation. (3) Mining m a c h i n e r y . (4) M i n e r a l d r e s s i n g . (5) W o r k e r s ' w e l f a r e and hygiene. E a c h s u b j e c t i s s u p e r v i s e d by a c o m m i t t e e of t h r e e m e m b e r s who have to: (a) d i s c u s s p r o p o s e d r e s e a r c h p r o j e c t s and b r i n g f o r w a r d r e c o m m e n d e d s u b j e c t s to the head c o m m i t t e e ; (b) m a k e p r o g r a m m e s and c a l c u l a t e c o s t s f o r the r e a l i z a t i o n of r e c o m m e n d e d p r o j e c t s ; (c) p r o p o s e m e m b e r s to the working c o m m i t t e e s ; (d) r e p o r t twice a y e a r a s u m m a r y of t h e c o m m i t t e e s within the s u b j e c t s group. E a c h p r o f e s s o r of t h e m i n i n g d i v i s i o n s i s g e n e r a l l y c h a i r m a n of h i s s u b j e c t g r o u p and a l s o of s o m e working c o m m i t t e e s .