Through analysis and generalization of more than 50 years of monitoring data pertaining to geomagnetic earthquake precursors in landfills across Uzbekistan involving repeated route and area surveys and stationary obse...Through analysis and generalization of more than 50 years of monitoring data pertaining to geomagnetic earthquake precursors in landfills across Uzbekistan involving repeated route and area surveys and stationary observations,as well as extensive data retrieved from the study of the complex in foreign countries,models of long-,medium-and short-term earthquake precursors were created for the first time.Medium-and short-term data were mainly studied based on monitoring data of the precursor complex considering geodynamic polygons in Uzbekistan.The analysis demonstrated that these precursors exhibit different shapes,configurations and signs.There occurred no uniform precursor form.Precursors exhibited bay-shaped forms,including both positive and negative signs,in addition to stepped,wave-oscillatory and other formats.The variety of manifestation forms primarily depends on the surrounding regions’geological and tectonic structures and the various processes in the Earth’s crust.展开更多
The evaluation of an intra-plate earthquake that occurred on Friday, 11th September, 2009 and felt in parts of Abeokuta, Ago-Iwoye, Ajambata, Ajegunle, Imeko, Ijebu-Ode, Ilaro and Ibadan, all in south western Nigeria ...The evaluation of an intra-plate earthquake that occurred on Friday, 11th September, 2009 and felt in parts of Abeokuta, Ago-Iwoye, Ajambata, Ajegunle, Imeko, Ijebu-Ode, Ilaro and Ibadan, all in south western Nigeria is presented. This event has been the largest inland earthquake recorded since the inception of digital seismological recording in Nigeria in 2008 was incepted. The event was recorded by three seismological stations operated by Centre for Geodesy and Geodynamics (CGG), Toro. Data obtained from the CGG stations and others distributed around the world were analysed to determine precise earthquake locations and focal mechanism and to assess the regional tectonic stress. The data recorded in MiniSEED format at a sampling rate of 40 samples per second (sps) were analyzed using the SEISAN earthquake analysis software. The resultshowed an epicentral location situated about 108 km west of Lagos, a focal depth of 10.0 km and an origin time of 03:10:21.60 GMT. The local and moment magnitudes were 4.5 and 4.2 respectively. The P-wave to S-wave velocity ratio was 1.72. The fault plane solutions obtained for the rupture process indicated that a normal dip-slip fault with median solution of strike 325°, dip 40° and rake?-90° was the probable trigger mechanism for this earthquake. It suggested that the event was a reactivation of a buried high-angle fault in the Precambrian basement represented by the contemporary northeast-southwest trending regional horizontal compressive stress. Generally, the seismotectonics of the region was linked to the fracture zones in the Atlantic Ocean.展开更多
This paper evaluates different characteristics for earthquake early warning. The scaling relationships between magnitude, epicenter distance and calculated parameters are derived from earthquake event data fi＇om USGS...This paper evaluates different characteristics for earthquake early warning. The scaling relationships between magnitude, epicenter distance and calculated parameters are derived from earthquake event data fi＇om USGS. The standard STA/LTA method is modified by adding two new parameters to eliminate the effects of the spike-type noise and small pulsetype noise ahead of the onset of the P-wave. After the detection of the P-wave, the algorithm extracts 12 kinds of parameters from the first 3 seconds of the P-wave. Then stepwise regression analysis of these parameters is performed to estimate the epicentral distance and magnitude. Six different parameters are selected to estimate the epicentral distance, and the median error for all 419 estimates is 16.5 krn. Four parameters are optimally combined to estimate the magnitude, and the mean error for all events is 0.0 magnitude units, with a standard deviation of 0.5. Finally, based on the estimation results, additional work is proposed to improve the accuracy of the results.展开更多
The 348 microearthquakes that occurred in Beijing and its neighboring areas(39°-41°,114°-117°E)during 1979 to March of 1992 are relocated in this study.Precision of hypocenter locations is improved...The 348 microearthquakes that occurred in Beijing and its neighboring areas(39°-41°,114°-117°E)during 1979 to March of 1992 are relocated in this study.Precision of hypocenter locations is improved by rechecking and supplementing readings of arriving times of the seismic phases used,testing and selecting the appropriate crustal model,and modifying the computer program.After the relocation,the number of earthquakes with focal depth determination has been increased to 313 from the previous 132.The overall average RMS residual of the observational arrival times has been reduced to 0.45±0.18 s from the previous value of 0.80±0.40 s.Nearly 10% of the relocated hypocenters,which are mostly in border regions of the area covered by the Beijing Telemetered Seismic Network,have been shifted more than 10 km.Epicenters of the relocated earthquakes are concentrated in the intermountainous basins,such as the Huai’an,Xuanhua,Huailai,and Zhuolu basins,and are related with the basin boundary faults between展开更多
The Region-Time-Length Algorithm (RTL algorithm) is introduced and improved in the paper. Compared with the original definition, the influence of rupture length on RTL function is emphasized and the weights of epicent...The Region-Time-Length Algorithm (RTL algorithm) is introduced and improved in the paper. Compared with the original definition, the influence of rupture length on RTL function is emphasized and the weights of epicentral distance function, time function, and rupture length function are ensured to be equal. The retrospective examinations of RTL algorithm in North China have indicated that the anomalies obtained by the improved RTL algorithm show the short or intermediate-short term precursory features in most cases. There are two types of RTL anomalous patterns before the main shock. For the I-type, the variation pattern of the VRTL, numerical values of the VRTL(x, y, z, t) function, is complete and most of them have shown the changing pattern of rising from 0 turning dropping or dropping from 0 turning rising. For the II-type, the variation pattern of VRTL is not complete, which increases or decreases quickly from 0 and there is no evident turning, the main shock generally occurs in the short period around the peak VRTL. The rising of VRTL indicates an increase of seismic activity relative to the background level, which means the enhancement of seismic activity, while the dropping of VRTL indicates the decrease of seismic activity relative to the background level, which represents the seismic quiescence to a certain extent. According to statistical examination results of RTL algorithm in North China, the methods to distinguish the intermediate and short-term anomalies and to estimate the occurrence time of the coming main shock are given in the paper. For both I and II-type RTL anomalies, the R-value, i.e., the forecasting score, is about 0.6 and 0.3 for the 3 months forecasting period and about 0.7 and 0.4 for the 6 months forecasting period. The preliminary discussion is also made for the influences of characteristic time-span t0, characteristic distance r0, and threshold magnitude M0 on computation of VRTL, as well as some other significant problems in application.展开更多
基金the financial support of the State Basic Research Development Program(2021)of the Committee for the Coordination of Science and Technology Development under the Ministry of Innovation of the Republic of Uzbekistan
文摘Through analysis and generalization of more than 50 years of monitoring data pertaining to geomagnetic earthquake precursors in landfills across Uzbekistan involving repeated route and area surveys and stationary observations,as well as extensive data retrieved from the study of the complex in foreign countries,models of long-,medium-and short-term earthquake precursors were created for the first time.Medium-and short-term data were mainly studied based on monitoring data of the precursor complex considering geodynamic polygons in Uzbekistan.The analysis demonstrated that these precursors exhibit different shapes,configurations and signs.There occurred no uniform precursor form.Precursors exhibited bay-shaped forms,including both positive and negative signs,in addition to stepped,wave-oscillatory and other formats.The variety of manifestation forms primarily depends on the surrounding regions’geological and tectonic structures and the various processes in the Earth’s crust.
文摘The evaluation of an intra-plate earthquake that occurred on Friday, 11th September, 2009 and felt in parts of Abeokuta, Ago-Iwoye, Ajambata, Ajegunle, Imeko, Ijebu-Ode, Ilaro and Ibadan, all in south western Nigeria is presented. This event has been the largest inland earthquake recorded since the inception of digital seismological recording in Nigeria in 2008 was incepted. The event was recorded by three seismological stations operated by Centre for Geodesy and Geodynamics (CGG), Toro. Data obtained from the CGG stations and others distributed around the world were analysed to determine precise earthquake locations and focal mechanism and to assess the regional tectonic stress. The data recorded in MiniSEED format at a sampling rate of 40 samples per second (sps) were analyzed using the SEISAN earthquake analysis software. The resultshowed an epicentral location situated about 108 km west of Lagos, a focal depth of 10.0 km and an origin time of 03:10:21.60 GMT. The local and moment magnitudes were 4.5 and 4.2 respectively. The P-wave to S-wave velocity ratio was 1.72. The fault plane solutions obtained for the rupture process indicated that a normal dip-slip fault with median solution of strike 325°, dip 40° and rake?-90° was the probable trigger mechanism for this earthquake. It suggested that the event was a reactivation of a buried high-angle fault in the Precambrian basement represented by the contemporary northeast-southwest trending regional horizontal compressive stress. Generally, the seismotectonics of the region was linked to the fracture zones in the Atlantic Ocean.
文摘This paper evaluates different characteristics for earthquake early warning. The scaling relationships between magnitude, epicenter distance and calculated parameters are derived from earthquake event data fi＇om USGS. The standard STA/LTA method is modified by adding two new parameters to eliminate the effects of the spike-type noise and small pulsetype noise ahead of the onset of the P-wave. After the detection of the P-wave, the algorithm extracts 12 kinds of parameters from the first 3 seconds of the P-wave. Then stepwise regression analysis of these parameters is performed to estimate the epicentral distance and magnitude. Six different parameters are selected to estimate the epicentral distance, and the median error for all 419 estimates is 16.5 krn. Four parameters are optimally combined to estimate the magnitude, and the mean error for all events is 0.0 magnitude units, with a standard deviation of 0.5. Finally, based on the estimation results, additional work is proposed to improve the accuracy of the results.
基金This project was sponsored by the State Science and TechnologyCommission and State Seismological Bureau (85-907-04-01),China.Contribution No.95A0051.Instirute ofGeophysics,SSB,China.
文摘The 348 microearthquakes that occurred in Beijing and its neighboring areas(39°-41°,114°-117°E)during 1979 to March of 1992 are relocated in this study.Precision of hypocenter locations is improved by rechecking and supplementing readings of arriving times of the seismic phases used,testing and selecting the appropriate crustal model,and modifying the computer program.After the relocation,the number of earthquakes with focal depth determination has been increased to 313 from the previous 132.The overall average RMS residual of the observational arrival times has been reduced to 0.45±0.18 s from the previous value of 0.80±0.40 s.Nearly 10% of the relocated hypocenters,which are mostly in border regions of the area covered by the Beijing Telemetered Seismic Network,have been shifted more than 10 km.Epicenters of the relocated earthquakes are concentrated in the intermountainous basins,such as the Huai’an,Xuanhua,Huailai,and Zhuolu basins,and are related with the basin boundary faults between
文摘The Region-Time-Length Algorithm (RTL algorithm) is introduced and improved in the paper. Compared with the original definition, the influence of rupture length on RTL function is emphasized and the weights of epicentral distance function, time function, and rupture length function are ensured to be equal. The retrospective examinations of RTL algorithm in North China have indicated that the anomalies obtained by the improved RTL algorithm show the short or intermediate-short term precursory features in most cases. There are two types of RTL anomalous patterns before the main shock. For the I-type, the variation pattern of the VRTL, numerical values of the VRTL(x, y, z, t) function, is complete and most of them have shown the changing pattern of rising from 0 turning dropping or dropping from 0 turning rising. For the II-type, the variation pattern of VRTL is not complete, which increases or decreases quickly from 0 and there is no evident turning, the main shock generally occurs in the short period around the peak VRTL. The rising of VRTL indicates an increase of seismic activity relative to the background level, which means the enhancement of seismic activity, while the dropping of VRTL indicates the decrease of seismic activity relative to the background level, which represents the seismic quiescence to a certain extent. According to statistical examination results of RTL algorithm in North China, the methods to distinguish the intermediate and short-term anomalies and to estimate the occurrence time of the coming main shock are given in the paper. For both I and II-type RTL anomalies, the R-value, i.e., the forecasting score, is about 0.6 and 0.3 for the 3 months forecasting period and about 0.7 and 0.4 for the 6 months forecasting period. The preliminary discussion is also made for the influences of characteristic time-span t0, characteristic distance r0, and threshold magnitude M0 on computation of VRTL, as well as some other significant problems in application.
