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Earthquakes and the cratonward limit of Iapetan faulting in eastern North America
GEOLOGY:EARTHQUAKES
309A
This paper emphasizes the consequences of the ordinal and qualitative nature of seismic intensity regarding its recording. The classical way of recording by an integer value implies that on many occasions it can be difficult to associate only one intensity degree to an event. Therefore, it is proposed to record the intensity in a new way so that the expert is no longer restricted to indicating only one value, but can express this belief that the considered event belongs to any one of the intensity classes in the scale. Following this approach, as an example, the completeness of the Sannio-Matese catalogue is studied and it is shown how the degree of completeness changes according to the degree of uncertainty in intensity assessment. (Authors)
The SIRENE macroseismic database has been utilized to draw isoseismal maps for the 140 best-documented French earthquakes, characterized by epieentral intensities of at least V (MSK) and located in all parts of the country. Focal depths of most of the events considered do not exceed about 10km. Their distribution correlates fairly well with regional dynamic geological features. A relationship is computed between magnitude, intensity and focal distanec. This relationship is applied to historical earthquakes contained in the database SIRENE which are characterised by their intensity only. These results are used in the evaluation as well deterministic as probabilistie of the seismic hazard on the national territory. (from Authors)
957047 Seismogeological and hydrological criteria for the new European macroseismic scale (MSK-92)
957051
J. Vogt, R. M. W. Musson & M. Stucchi, Natural Hazards, 10(1-2), 1994, pp 1-6. In 1988, an ESC Working Group 'Mucroseismie Scales' started upgrading the MSK-81 Intensity Seaie. This paper presents the background and decisions made with respect to the so-called seismogeological effects. Discussion has pointed out that they cannot be treated and used in the same way as the effects of humans, objects and buildings, for many reasons. Therefore, the W G adopted the solution of using such effects as a side tool for intensity assessment, providing a comprehensive table where the experimental relations between seismogeological effects and intensity degrees assessed by means of other effects - are presented. (Authors)
957048 Earthquakes and the crntonward limit of Iapetan faulting in eastern North America R. L. Wheeler, Geology, 23(2), 1995, pp 105-108. The eratonward limit of large normal faults in the passive margin of the Late Proterozoie to early Paleozoic Iapetus Ocean is a fundamental boundary for the assessment of seismic hazards in populous eastern North America. Earthquakes at five localities in the Iapetan margin have been attributed to compressional reaction of Iapetan normal faults. The northwesternmost locations of known Iapetan faults, both seismic and currently aseismic, lie along a line from Labrador to Alabama. This line coincides approximately with the northwestward transition from a more seismically active continental rim to a generally less active eratonie interior. Thus, the northwestern boundary of Iapetan faults separates two large regions of mostly different seismic hazard. (Author)
957049 Corrimientos dentro del subsuelo lacnstre de la cuenca de Mexico
(Displacement of lacustrine subsoil in the Mexican Basin) J. Durazo, Geofisica Internacional, 33(4), 1994, pp 625-634. Detectable horizontal differential displacements can occur in the shallow lake sediments in the basin of Mexico. The clue is generalized obstruction at the same depth (mainly between 5 to 10 m) in flexible-tube piezometers, documented at 18 different sites. Obstructions were detected by means of a cable. Field work was carried out a few days after the September 19, 1985 earthquake (Ms = 8.1). The generalized obstruction cannot be explained by land subsidence but could be related to the general seismic behavior of the basin. (English summary)
957050 Atlas of macroseismic maps for French earthquakes with their principal characteristics A. Levret, J. C. Backe & M. Cushing, Natural Hazards, 10(1-2), 1994, pp 19-46.
Seismic hazard assessment in Jordan and its vicinity E. AI-Tarazi, Natural Hazards, 10(1-2), 1994, pp 79-96. Seismic hazard assessment plays an important role in seismic design decisions concerning civil engineering constructions such as dams, tall buildings, and nuclear power plants. The rate of seismic activity in Jordan and its vicinity is moderate, however, strong earthquakes have occurred in the past and some of them have caused many casualities and much destruction over large areas. The earthquake hazard in Jordan and its vicinity is assessed on the basis of probabilistic methods. For this purpose, an updated earthquake catalog is compiled which covers the period between AD 1-1989. Thirteen seismic zones are defined on a regional seismic and tectonic map presented for the area. The results of the seismic hazard assessment are displayed as iso-acceleration contours expected to be exceeded during typical economic life times of structures, i.e. 50 and 100 years. For each model, two seismic hazard maps are derived. (from Author)
957052 A geophysical approach to the problem of seismicity in the Indian Shield A. G. B. Reddi, Journal- Geological Society of India, 45(1), 1995, pp 5-17. An earthquake is a culmination of stress build-ups that go on over a period of time at various brittle-ductile transitions located mainly within the crust. Mapping such transitions must therefore form an integral part of any effort at understanding the seismicity of a region. However, this aspect has been grossly neglected, most concerns so far revolving round faults and allied structures that only provide a mechanism for stress dissipation as distinguished from stress accumulation. Any holistic approach to the problem must include an investigation of the thickness and composition of the crust on the one hand and surface heat flow on the other, since these are known to have a direct bearing on the seismic propensity of a region. Gravity maps could provide a basis for effective selection of areas for detailed follow-up by more complex methods. Adopting this principle, a broad geophysical strategy has been mooted for the active consideration of geoscientists. (from Author)
957053 Correlation analysis of percentage of collapsing houses and seismic intensity of Tangshan earthquake (in Chinese) Yang Zhe & Cheng Jiayu, Seismology & Geology, 16(3), 1994, pp 283-288. The percentage of houses which collapsed because of the Tangshan earthquake was interpreted from aerial photographs taken after the shock. The regression curve of the percentage of collapsing houses and seismic intensity was formulated. The frequency of the percentage of collapsing houses in each intensity was also calculated, which provides a numerical method for estimation of earthquake losses. (from English summary)
309A
This paper emphasizes the consequences of the ordinal and qualitative nature of seismic intensity regarding its recording. The classical way of recording by an integer value implies that on many occasions it can be difficult to associate only one intensity degree to an event. Therefore, it is proposed to record the intensity in a new way so that the expert is no longer restricted to indicating only one value, but can express this belief that the considered event belongs to any one of the intensity classes in the scale. Following this approach, as an example, the completeness of the Sannio-Matese catalogue is studied and it is shown how the degree of completeness changes according to the degree of uncertainty in intensity assessment. (Authors)
The SIRENE macroseismic database has been utilized to draw isoseismal maps for the 140 best-documented French earthquakes, characterized by epieentral intensities of at least V (MSK) and located in all parts of the country. Focal depths of most of the events considered do not exceed about 10km. Their distribution correlates fairly well with regional dynamic geological features. A relationship is computed between magnitude, intensity and focal distanec. This relationship is applied to historical earthquakes contained in the database SIRENE which are characterised by their intensity only. These results are used in the evaluation as well deterministic as probabilistie of the seismic hazard on the national territory. (from Authors)
957047 Seismogeological and hydrological criteria for the new European macroseismic scale (MSK-92)
957051
J. Vogt, R. M. W. Musson & M. Stucchi, Natural Hazards, 10(1-2), 1994, pp 1-6. In 1988, an ESC Working Group 'Mucroseismie Scales' started upgrading the MSK-81 Intensity Seaie. This paper presents the background and decisions made with respect to the so-called seismogeological effects. Discussion has pointed out that they cannot be treated and used in the same way as the effects of humans, objects and buildings, for many reasons. Therefore, the W G adopted the solution of using such effects as a side tool for intensity assessment, providing a comprehensive table where the experimental relations between seismogeological effects and intensity degrees assessed by means of other effects - are presented. (Authors)
957048 Earthquakes and the crntonward limit of Iapetan faulting in eastern North America R. L. Wheeler, Geology, 23(2), 1995, pp 105-108. The eratonward limit of large normal faults in the passive margin of the Late Proterozoie to early Paleozoic Iapetus Ocean is a fundamental boundary for the assessment of seismic hazards in populous eastern North America. Earthquakes at five localities in the Iapetan margin have been attributed to compressional reaction of Iapetan normal faults. The northwesternmost locations of known Iapetan faults, both seismic and currently aseismic, lie along a line from Labrador to Alabama. This line coincides approximately with the northwestward transition from a more seismically active continental rim to a generally less active eratonie interior. Thus, the northwestern boundary of Iapetan faults separates two large regions of mostly different seismic hazard. (Author)
957049 Corrimientos dentro del subsuelo lacnstre de la cuenca de Mexico
(Displacement of lacustrine subsoil in the Mexican Basin) J. Durazo, Geofisica Internacional, 33(4), 1994, pp 625-634. Detectable horizontal differential displacements can occur in the shallow lake sediments in the basin of Mexico. The clue is generalized obstruction at the same depth (mainly between 5 to 10 m) in flexible-tube piezometers, documented at 18 different sites. Obstructions were detected by means of a cable. Field work was carried out a few days after the September 19, 1985 earthquake (Ms = 8.1). The generalized obstruction cannot be explained by land subsidence but could be related to the general seismic behavior of the basin. (English summary)
957050 Atlas of macroseismic maps for French earthquakes with their principal characteristics A. Levret, J. C. Backe & M. Cushing, Natural Hazards, 10(1-2), 1994, pp 19-46.
Seismic hazard assessment in Jordan and its vicinity E. AI-Tarazi, Natural Hazards, 10(1-2), 1994, pp 79-96. Seismic hazard assessment plays an important role in seismic design decisions concerning civil engineering constructions such as dams, tall buildings, and nuclear power plants. The rate of seismic activity in Jordan and its vicinity is moderate, however, strong earthquakes have occurred in the past and some of them have caused many casualities and much destruction over large areas. The earthquake hazard in Jordan and its vicinity is assessed on the basis of probabilistic methods. For this purpose, an updated earthquake catalog is compiled which covers the period between AD 1-1989. Thirteen seismic zones are defined on a regional seismic and tectonic map presented for the area. The results of the seismic hazard assessment are displayed as iso-acceleration contours expected to be exceeded during typical economic life times of structures, i.e. 50 and 100 years. For each model, two seismic hazard maps are derived. (from Author)
957052 A geophysical approach to the problem of seismicity in the Indian Shield A. G. B. Reddi, Journal- Geological Society of India, 45(1), 1995, pp 5-17. An earthquake is a culmination of stress build-ups that go on over a period of time at various brittle-ductile transitions located mainly within the crust. Mapping such transitions must therefore form an integral part of any effort at understanding the seismicity of a region. However, this aspect has been grossly neglected, most concerns so far revolving round faults and allied structures that only provide a mechanism for stress dissipation as distinguished from stress accumulation. Any holistic approach to the problem must include an investigation of the thickness and composition of the crust on the one hand and surface heat flow on the other, since these are known to have a direct bearing on the seismic propensity of a region. Gravity maps could provide a basis for effective selection of areas for detailed follow-up by more complex methods. Adopting this principle, a broad geophysical strategy has been mooted for the active consideration of geoscientists. (from Author)
957053 Correlation analysis of percentage of collapsing houses and seismic intensity of Tangshan earthquake (in Chinese) Yang Zhe & Cheng Jiayu, Seismology & Geology, 16(3), 1994, pp 283-288. The percentage of houses which collapsed because of the Tangshan earthquake was interpreted from aerial photographs taken after the shock. The regression curve of the percentage of collapsing houses and seismic intensity was formulated. The frequency of the percentage of collapsing houses in each intensity was also calculated, which provides a numerical method for estimation of earthquake losses. (from English summary)