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Catalog errors and the M8 earthquake prediction algorithm
GEOLOGY:EARTHQUAKES In semi-arid New South Wales, large areas of red duplex soils were scalded bv. wind and water erosion exacerbated by overgrazing and drought, leaving them devoid of vegetation. On slones of less than 0.5%. waternonds (about 0.5 ha) enclosed by horseshoe shaped ‘banks have been successful in reclaiming scalds. The macro- and micromorphology and chemical and physical properties of profiles under scald and under 7 month old and 22 year old waterponds were compared. It was concluded that early stages of revegetation resulted from water retention and later stages from improved infiltration due to restructuring the B horizon accompanied by formation of large cracks. Restructuring resulted from destabilizing the clay which remained sodic after leaching or soluble salts. Although leaching is rapid, restructuring takes several years, possibly due to the absence of any mechanical input. (Authors)
Earthquake mechanisms and effects 955032 Study on the approach to predict earthquakes based on crustal deformation (in Chinese) Wang Chuanhua, Earthquake (Beijing), 4(4), 1994, pp Sl58. By applying the theory of systematic science, the crustal deformation network in Hebei province and its adjacent regions is regarded as an entire prediction system and by means of comprehensive analysis of the results obtained from the practical PDBS software system, in this paper the anomaly deformation index, representing the integral compatible state of the system, was proposed, which could be used to predict earthquakes in the area. (from English summary) 955033 Long-term earthquake prediction in tbe North Pacific seismic zone based on the time and magnitude predictable mode1 E. E. Papadimitriou, Natural Hazards, 9(3), 1994, pp 303321. Earthquake recurrence intervals for large and great shallow mainshocks in 12 seismogenic sources along the North Pacific seismic zone (Alaska-Aleutians-Kamchatka-Kuril Islands) have been estimated and used for the determination of the following relations: log Tt = 0.30 Mti + 0.15 M - 0.27 log M, + 5.24; and Mr = 1.05 Mmin - 0.47 iUp + O.&I log M, 12.39, where Tt is the interevent time, measured in years, Mh the surface wave magnitude of the smallest mainstock considered, Mp the magnitude of the preceding mainshock, Mr the magnitude of the following mainshock, M,, the moment rate in each source per year. The positive dependence of Tt on the Ma implies that the time-predictable model is valid for the area under examination, a very interesting property, since it contributes to the realistic progress toward the long-term prediction of earthquakes. (from Author) 955034 Catalog errors and the M8 eartbquake prediction algoritkm R. E. Habermann 8c F. Creamer, Bulletin - Seismological Society of America, 84(5), 1994, pp 1551-1559. The earthquake prediction algorithm M8 has been tested using five different seismicity data sets for the southwest Pacific. It is demonstrated that the alarms identified by M8 are strongly dependent on the seismicity catalog used. The alarms occur preferentially during times when magnitudes are relatively high because of systematic errors. These alarms cannot be reasonably interpreted as precursors to earthquakes or any other real change in the Earth without first understanding and correcting the errors in the seismicity catalogs. This study highlights the need for improving the
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quality of geophysical data, which is presently unsuitable for many studies related to earthquake prediction. (from Authors) 955035 Recursive stochastic deconvolution in the estimation of earthquake source parameters: synthetic waveforms J. Qu & T. L. Teng, Physics of the Earth & Planetary Interiors, 86(4), 1994, pp 301-327.
A method of the linear minimum mean-squares error (LMMSE) solution for source inversion is presented in terms of a recursive algorithm. A covariance matrix of estimation error, as well as a resolution matrix are also computed through recursion. It is shown that this recursive solution corresponds to a stationary Kahnan Bltering estimation for a linear dynamic system, which makes it possible to perform satisfactorily in an environment where complete knowledge of the relevant signal characteristics is not available. This method is tested by examining the Sierra Madre earthquake June 1991, California. (from Authors) 955036 Teleseismic search for slow precursors to large ear&quakes P. F. Ihmle & T. H. Jordan, Science, 266(5190), 1994, pp 1547-1551. Some large earthquakes display low-frequency seismic anomalies that are best explained by episodes of slow, smooth deformation immediately before their high-frequency origin times. Analysis of the low-frequency spectra of 107 shallow-focus earthquakes revealed 20 events that had slow precursors; 19 were slow earthquakes associated with the ocean ridge-transform system, and 1 was a slow earthquake on an intracontinental transform fault in the East African Rift system. These anomalous earthquakes appear to be compound events, each comprising one or more ordinary (fast) ruptures in the shallow seismogenic zone initiated by a precursory slow event in the adjacent or subjacent lithosphere. (Authors) 955037 Common cyclicities ins the seismicity and water level fluctuations at tke Charlevoix seismic zone on the St Lawrence River, Quebec, Canada G. P. Tsofhas, G. A. Bollinger & J. K. Costain, Journal of Geodynumics, 19(2), 1994, pp 117-139. Intraplate seismic&y has no widely accepted explanation for its origin. The hydroseismicity hypothesis suggests that natural increases in hydraulic head, caused by transient increases in water table elevation, can be transmitted to hypocentral depths (lo-25 km) in a fractured, prestressed, near-failure crust, and, along with long term hydrolytic weakening of rocks, contribute to the triggering of earthquakes. In this study, the temporal characteristics of seismicity and water level fluctuations at the Charlevoiz seismic zone on the Saint Lawrence River in Quebec, Canada, are determined using Fourier spectral analysis and are investigated for possible temporal relationships, as predicted by hydroseismicity, using group delay analysis. (from Authors) 955038 Analysis of seismic intensities observed in Israel L. Feldman & A. Shapira, Natural Hazarrls, 9(3), 1994, pp 287-301. Using macroseismic observations in Israel following distantearthquakes and by using the empirical attenuation function obtained, an attempt is made to identify areas within Israel with unusual response. The results indicate a poor correlation between the intensity response of a site and its geological and geotechnical properties. (from Authors)
Earthquake mechanisms and effects 955032 Study on the approach to predict earthquakes based on crustal deformation (in Chinese) Wang Chuanhua, Earthquake (Beijing), 4(4), 1994, pp Sl58. By applying the theory of systematic science, the crustal deformation network in Hebei province and its adjacent regions is regarded as an entire prediction system and by means of comprehensive analysis of the results obtained from the practical PDBS software system, in this paper the anomaly deformation index, representing the integral compatible state of the system, was proposed, which could be used to predict earthquakes in the area. (from English summary) 955033 Long-term earthquake prediction in tbe North Pacific seismic zone based on the time and magnitude predictable mode1 E. E. Papadimitriou, Natural Hazards, 9(3), 1994, pp 303321. Earthquake recurrence intervals for large and great shallow mainshocks in 12 seismogenic sources along the North Pacific seismic zone (Alaska-Aleutians-Kamchatka-Kuril Islands) have been estimated and used for the determination of the following relations: log Tt = 0.30 Mti + 0.15 M - 0.27 log M, + 5.24; and Mr = 1.05 Mmin - 0.47 iUp + O.&I log M, 12.39, where Tt is the interevent time, measured in years, Mh the surface wave magnitude of the smallest mainstock considered, Mp the magnitude of the preceding mainshock, Mr the magnitude of the following mainshock, M,, the moment rate in each source per year. The positive dependence of Tt on the Ma implies that the time-predictable model is valid for the area under examination, a very interesting property, since it contributes to the realistic progress toward the long-term prediction of earthquakes. (from Author) 955034 Catalog errors and the M8 eartbquake prediction algoritkm R. E. Habermann 8c F. Creamer, Bulletin - Seismological Society of America, 84(5), 1994, pp 1551-1559. The earthquake prediction algorithm M8 has been tested using five different seismicity data sets for the southwest Pacific. It is demonstrated that the alarms identified by M8 are strongly dependent on the seismicity catalog used. The alarms occur preferentially during times when magnitudes are relatively high because of systematic errors. These alarms cannot be reasonably interpreted as precursors to earthquakes or any other real change in the Earth without first understanding and correcting the errors in the seismicity catalogs. This study highlights the need for improving the
205A
quality of geophysical data, which is presently unsuitable for many studies related to earthquake prediction. (from Authors) 955035 Recursive stochastic deconvolution in the estimation of earthquake source parameters: synthetic waveforms J. Qu & T. L. Teng, Physics of the Earth & Planetary Interiors, 86(4), 1994, pp 301-327.
A method of the linear minimum mean-squares error (LMMSE) solution for source inversion is presented in terms of a recursive algorithm. A covariance matrix of estimation error, as well as a resolution matrix are also computed through recursion. It is shown that this recursive solution corresponds to a stationary Kahnan Bltering estimation for a linear dynamic system, which makes it possible to perform satisfactorily in an environment where complete knowledge of the relevant signal characteristics is not available. This method is tested by examining the Sierra Madre earthquake June 1991, California. (from Authors) 955036 Teleseismic search for slow precursors to large ear&quakes P. F. Ihmle & T. H. Jordan, Science, 266(5190), 1994, pp 1547-1551. Some large earthquakes display low-frequency seismic anomalies that are best explained by episodes of slow, smooth deformation immediately before their high-frequency origin times. Analysis of the low-frequency spectra of 107 shallow-focus earthquakes revealed 20 events that had slow precursors; 19 were slow earthquakes associated with the ocean ridge-transform system, and 1 was a slow earthquake on an intracontinental transform fault in the East African Rift system. These anomalous earthquakes appear to be compound events, each comprising one or more ordinary (fast) ruptures in the shallow seismogenic zone initiated by a precursory slow event in the adjacent or subjacent lithosphere. (Authors) 955037 Common cyclicities ins the seismicity and water level fluctuations at tke Charlevoix seismic zone on the St Lawrence River, Quebec, Canada G. P. Tsofhas, G. A. Bollinger & J. K. Costain, Journal of Geodynumics, 19(2), 1994, pp 117-139. Intraplate seismic&y has no widely accepted explanation for its origin. The hydroseismicity hypothesis suggests that natural increases in hydraulic head, caused by transient increases in water table elevation, can be transmitted to hypocentral depths (lo-25 km) in a fractured, prestressed, near-failure crust, and, along with long term hydrolytic weakening of rocks, contribute to the triggering of earthquakes. In this study, the temporal characteristics of seismicity and water level fluctuations at the Charlevoiz seismic zone on the Saint Lawrence River in Quebec, Canada, are determined using Fourier spectral analysis and are investigated for possible temporal relationships, as predicted by hydroseismicity, using group delay analysis. (from Authors) 955038 Analysis of seismic intensities observed in Israel L. Feldman & A. Shapira, Natural Hazarrls, 9(3), 1994, pp 287-301. Using macroseismic observations in Israel following distantearthquakes and by using the empirical attenuation function obtained, an attempt is made to identify areas within Israel with unusual response. The results indicate a poor correlation between the intensity response of a site and its geological and geotechnical properties. (from Authors)