In this paper, the relation that the curves of nonlinear parameter H and its difference Δ H bear with strong earthquakes in North China has been studied. First, the RSH algorithm has been applied to the North ...In this paper, the relation that the curves of nonlinear parameter H and its difference Δ H bear with strong earthquakes in North China has been studied. First, the RSH algorithm has been applied to the North China region; the schemes of six quantitative prediction indexes have been studied in detail and then tested by tracing back predictions. The result shows that all the six prediction schemes are of certain prediction efficiency and have passed the test. Among the six schemes, A and E are of the best effect, with correlation coefficients R of 0.47 and 0.48 respectively. We recommend these two schemes for practical use in prediction in the future. Furthermore, the relation between the curve of Δ H (the difference of H) and strong earthquake has been studied. Based on the above results, the RSΔH algorithm that uses the Δ H value to predict strong earthquake has been put forward and applied to predict strong earthquakes in North China. The correlation coefficient R of tracing back prediction by this method is 0.45; this means that this method is also of better prediction efficiency. A combined application of these two algorithms has also been proposed. By the combined method, the time length spanned by false predictions can be shortened and thus the R value can be raised.展开更多
The capability of accurately predicting mineralogical brittleness index (BI) from basic suites of well logs is desirable as it provides a useful indicator of the fracability of tight formations.Measuring mineralogical...The capability of accurately predicting mineralogical brittleness index (BI) from basic suites of well logs is desirable as it provides a useful indicator of the fracability of tight formations.Measuring mineralogical components in rocks is expensive and time consuming.However,the basic well log curves are not well correlated with BI so correlation-based,machine-learning methods are not able to derive highly accurate BI predictions using such data.A correlation-free,optimized data-matching algorithm is configured to predict BI on a supervised basis from well log and core data available from two published wells in the Lower Barnett Shale Formation (Texas).This transparent open box (TOB) algorithm matches data records by calculating the sum of squared errors between their variables and selecting the best matches as those with the minimum squared errors.It then applies optimizers to adjust weights applied to individual variable errors to minimize the root mean square error (RMSE)between calculated and predicted (BI).The prediction accuracy achieved by TOB using just five well logs (Gr,ρb,Ns,Rs,Dt) to predict BI is dependent on the density of data records sampled.At a sampling density of about one sample per 0.5 ft BI is predicted with RMSE~0.056 and R^(2)~0.790.At a sampling density of about one sample per0.1 ft BI is predicted with RMSE~0.008 and R^(2)~0.995.Adding a stratigraphic height index as an additional (sixth)input variable method improves BI prediction accuracy to RMSE~0.003 and R^(2)~0.999 for the two wells with only 1 record in 10,000 yielding a BI prediction error of>±0.1.The model has the potential to be applied in an unsupervised basis to predict BI from basic well log data in surrounding wells lacking mineralogical measurements but with similar lithofacies and burial histories.The method could also be extended to predict elastic rock properties in and seismic attributes from wells and seismic data to improve the precision of brittleness index and fracability mapping spatially.展开更多
The observation of geomagnetic field variations is an important approach to studying earthquake precursors.Since 1987,the China Earthquake Administration has explored this seismomagnetic relationship.In particular,the...The observation of geomagnetic field variations is an important approach to studying earthquake precursors.Since 1987,the China Earthquake Administration has explored this seismomagnetic relationship.In particular,they studied local magnetic field anomalies over the Chinese mainland for earthquake prediction.Owing to the years of research on the seismomagnetic relationship,earthquake prediction experts have concluded that the compressive magnetic effect,tectonic magnetic effect,electric magnetic fluid effect,and other factors contribute to preearthquake magnetic anomalies.However,this involves a small magnitude of magnetic field changes.It is difficult to relate them to the abnormal changes of the extremely large magnetic field in regions with extreme earthquakes owing to the high cost of professional geomagnetic equipment,thereby limiting large-scale deployment.Moreover,it is difficult to obtain strong magnetic field changes before an earthquake.The Tianjin Earthquake Agency has developed low-cost geomagnetic field observation equipment through the Beijing–Tianjin–Hebei geomagnetic equipment test project.The new system was used to test the availability of equipment and determine the findings based on big data..展开更多
The improved calculation method of b value is presented in tills paper. The method can enlarge the role of earthquake occurrence frequency in b value calculation and thus increase the b value variation amplitude. In t...The improved calculation method of b value is presented in tills paper. The method can enlarge the role of earthquake occurrence frequency in b value calculation and thus increase the b value variation amplitude. In this case,the combination structure variation between earthquake magnitudes and corresponding frequencies could be shown clearly. According to the calculation and analysis for limited mainshocks in the complete seismicity data of selected monitored area with assigned consistent lowest magnitude, the precursor anomaly features, quantitative indexes and the calculation formula of relative subject function of b value variation have been preliminarily worked out. The prediction in short period (from 1 to 3 months) for damage earthquakes in the monitored area mentioned above can be put forward on the basis of the results of quantitative calculation and analysis.展开更多
Since 1949, Chinese scientists have successfully predicted occurrence of many major earthquakes, such as the Haicheng MT. 3 event in 1975 and the Asian Game Village shock of 1990. In recent 20 years, however, some sei...Since 1949, Chinese scientists have successfully predicted occurrence of many major earthquakes, such as the Haicheng MT. 3 event in 1975 and the Asian Game Village shock of 1990. In recent 20 years, however, some seis-mologists abroad have taken a disappointed and pessimistic view to earthquake prediction because of several failures. They suggest that the efforts should turn toward other fields, such as identification of building＇ s earthquake-proof capability, enhancement of house strength, and development of precise observational systems which will facilitate fast loca- ting of future major temblors and emergent relief on site. Such a pessimistic feeling has also influenced some Chinese researchers of the seismological community who attempted to give up efforts for earthquake prediction. Meanwhile other scientific workers are insisting in experiments and practices in this field and achieved some inspiring results. In this paper, we present several representative cases to illustrate that earthquakes are predictable under some conditions.展开更多
Seismic damage indices of structure are widely used to quantificationally analyze structural damage levels under earthquake action. In this paper, a five-storey building model and a seventeen-storey building model are...Seismic damage indices of structure are widely used to quantificationally analyze structural damage levels under earthquake action. In this paper, a five-storey building model and a seventeen-storey building model are established. According to seven typical indices and different earthquake-inputs, a structural damage prediction is performed, with the results showing serious uncertainty of structural damage prediction due to different indices. Understanding of this phenomenon aids the comprehension and application of the results of earthquake damage prediction.展开更多
Deca</span><span style="font-family:Verdana;">dal forerunning seismic activity is examined for very large, shall</span><span style="font-family:Verdana;">ow earthquakes alon...Deca</span><span style="font-family:Verdana;">dal forerunning seismic activity is examined for very large, shall</span><span style="font-family:Verdana;">ow earthquakes along strike-slip and intraplate faults of the world. It includes forerunning shocks of magnitude Mw ≥ 5.0 for 21 mainshocks of Mw 7.5 to 8.6 from 1989 to 2020. Much forerunning activity occurred at what are interpreted to be smaller asperities along the peripheries of the rupture zones of great mainshocks at transform faults and subduction zones. Several great asperities as ascertained from forerunning activity agree with the areas of high seism</span><span style="font-family:Verdana;">ic slip as determined by others using geodetic, mapping of surf</span><span style="font-family:Verdana;">ace faulting, and finite-source seismic modeling. The zones of high slip in many great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities. Asperities are strong, well-coupled portions of plate interfaces. Different patterns of forerunning activity on time scales of up to 45 years are attributed to the sizes and spacing of asperities (or lack of). This permits at least some great asperities along transform faults to be mapped decades before they rupture in great shocks. Rupture zones of many great mainshocks along transform faults are bordered either along strike, at depth or regionally by zones of lower plate coupling including either fault creep</span></span><span style="font-family:""> </span><span style="font-family:Verdana;"> forerunning activity, aftershocks and/or slow-slip events. Forerunning activity to transforms in continental areas is more widespread spatially than that adjacent to oceanic transforms. The parts of the San Andreas fault themselves that ruptured in great California earthquakes during 1812, 1857 and 1906 have been very quiet since 1920;moderate to large shocks have been concentrated on their peripheries. The intraplate shocks studied, however, exhibited few if any forerunning events, which is attributed to the short period of time studied compared to their repeat times. The detection of forerunning and precursory activities for various time scales should be sought on the peripheries of great asperities and not just along the major faults themselves. This paper compliments that on decadal forerunning activity to great and giant earthquakes along subduction zones.展开更多
The Zhangjiakou-Penglai fault zone lies in the northern part of North China Plain and extends along the Zhangjiakou-Huailai-Sanhe-Tianjin-Bohai Sea-Penglai-Yantai-North Huanghai Sea line, it is about 900 km long and s...The Zhangjiakou-Penglai fault zone lies in the northern part of North China Plain and extends along the Zhangjiakou-Huailai-Sanhe-Tianjin-Bohai Sea-Penglai-Yantai-North Huanghai Sea line, it is about 900 km long and some 250-km wide in a northwest direction. The 1679 Sanhe-Pinggu M 8.0 and the 1976 Tangshan M7.8 earthquakes occurred in the fault zone. In this paper an analysis of Gutenberg- Richter’s empirical relation and time process of historic and recent earthquakes along the eastern and western segments of the fault zone separated by the 117°line indicates that they obey a Poison process and, hence, a calculation from it yields a cumulative probability of strong earthquake occurrence along the two segments before 2010, i. e. the probability of M6.0 earthquake occurrence is 0.80 along the eastern segment and the probability of M7. 0 earthquake occurrence is 0.76 along the western segment of the fault zone.展开更多
文摘In this paper, the relation that the curves of nonlinear parameter H and its difference Δ H bear with strong earthquakes in North China has been studied. First, the RSH algorithm has been applied to the North China region; the schemes of six quantitative prediction indexes have been studied in detail and then tested by tracing back predictions. The result shows that all the six prediction schemes are of certain prediction efficiency and have passed the test. Among the six schemes, A and E are of the best effect, with correlation coefficients R of 0.47 and 0.48 respectively. We recommend these two schemes for practical use in prediction in the future. Furthermore, the relation between the curve of Δ H (the difference of H) and strong earthquake has been studied. Based on the above results, the RSΔH algorithm that uses the Δ H value to predict strong earthquake has been put forward and applied to predict strong earthquakes in North China. The correlation coefficient R of tracing back prediction by this method is 0.45; this means that this method is also of better prediction efficiency. A combined application of these two algorithms has also been proposed. By the combined method, the time length spanned by false predictions can be shortened and thus the R value can be raised.
文摘The capability of accurately predicting mineralogical brittleness index (BI) from basic suites of well logs is desirable as it provides a useful indicator of the fracability of tight formations.Measuring mineralogical components in rocks is expensive and time consuming.However,the basic well log curves are not well correlated with BI so correlation-based,machine-learning methods are not able to derive highly accurate BI predictions using such data.A correlation-free,optimized data-matching algorithm is configured to predict BI on a supervised basis from well log and core data available from two published wells in the Lower Barnett Shale Formation (Texas).This transparent open box (TOB) algorithm matches data records by calculating the sum of squared errors between their variables and selecting the best matches as those with the minimum squared errors.It then applies optimizers to adjust weights applied to individual variable errors to minimize the root mean square error (RMSE)between calculated and predicted (BI).The prediction accuracy achieved by TOB using just five well logs (Gr,ρb,Ns,Rs,Dt) to predict BI is dependent on the density of data records sampled.At a sampling density of about one sample per 0.5 ft BI is predicted with RMSE~0.056 and R^(2)~0.790.At a sampling density of about one sample per0.1 ft BI is predicted with RMSE~0.008 and R^(2)~0.995.Adding a stratigraphic height index as an additional (sixth)input variable method improves BI prediction accuracy to RMSE~0.003 and R^(2)~0.999 for the two wells with only 1 record in 10,000 yielding a BI prediction error of>±0.1.The model has the potential to be applied in an unsupervised basis to predict BI from basic well log data in surrounding wells lacking mineralogical measurements but with similar lithofacies and burial histories.The method could also be extended to predict elastic rock properties in and seismic attributes from wells and seismic data to improve the precision of brittleness index and fracability mapping spatially.
基金supported by the Spark Program of Earthquake Science and Technology(No.XH23003C).
文摘The observation of geomagnetic field variations is an important approach to studying earthquake precursors.Since 1987,the China Earthquake Administration has explored this seismomagnetic relationship.In particular,they studied local magnetic field anomalies over the Chinese mainland for earthquake prediction.Owing to the years of research on the seismomagnetic relationship,earthquake prediction experts have concluded that the compressive magnetic effect,tectonic magnetic effect,electric magnetic fluid effect,and other factors contribute to preearthquake magnetic anomalies.However,this involves a small magnitude of magnetic field changes.It is difficult to relate them to the abnormal changes of the extremely large magnetic field in regions with extreme earthquakes owing to the high cost of professional geomagnetic equipment,thereby limiting large-scale deployment.Moreover,it is difficult to obtain strong magnetic field changes before an earthquake.The Tianjin Earthquake Agency has developed low-cost geomagnetic field observation equipment through the Beijing–Tianjin–Hebei geomagnetic equipment test project.The new system was used to test the availability of equipment and determine the findings based on big data..
文摘The improved calculation method of b value is presented in tills paper. The method can enlarge the role of earthquake occurrence frequency in b value calculation and thus increase the b value variation amplitude. In this case,the combination structure variation between earthquake magnitudes and corresponding frequencies could be shown clearly. According to the calculation and analysis for limited mainshocks in the complete seismicity data of selected monitored area with assigned consistent lowest magnitude, the precursor anomaly features, quantitative indexes and the calculation formula of relative subject function of b value variation have been preliminarily worked out. The prediction in short period (from 1 to 3 months) for damage earthquakes in the monitored area mentioned above can be put forward on the basis of the results of quantitative calculation and analysis.
文摘Since 1949, Chinese scientists have successfully predicted occurrence of many major earthquakes, such as the Haicheng MT. 3 event in 1975 and the Asian Game Village shock of 1990. In recent 20 years, however, some seis-mologists abroad have taken a disappointed and pessimistic view to earthquake prediction because of several failures. They suggest that the efforts should turn toward other fields, such as identification of building＇ s earthquake-proof capability, enhancement of house strength, and development of precise observational systems which will facilitate fast loca- ting of future major temblors and emergent relief on site. Such a pessimistic feeling has also influenced some Chinese researchers of the seismological community who attempted to give up efforts for earthquake prediction. Meanwhile other scientific workers are insisting in experiments and practices in this field and achieved some inspiring results. In this paper, we present several representative cases to illustrate that earthquakes are predictable under some conditions.
基金sponsored by the National Basic Research Programof China (2006BAC13B02)the Science and Technology Special Program for Seismology, China Earthquake Administration (200708003)
文摘Seismic damage indices of structure are widely used to quantificationally analyze structural damage levels under earthquake action. In this paper, a five-storey building model and a seventeen-storey building model are established. According to seven typical indices and different earthquake-inputs, a structural damage prediction is performed, with the results showing serious uncertainty of structural damage prediction due to different indices. Understanding of this phenomenon aids the comprehension and application of the results of earthquake damage prediction.
文摘Deca</span><span style="font-family:Verdana;">dal forerunning seismic activity is examined for very large, shall</span><span style="font-family:Verdana;">ow earthquakes along strike-slip and intraplate faults of the world. It includes forerunning shocks of magnitude Mw ≥ 5.0 for 21 mainshocks of Mw 7.5 to 8.6 from 1989 to 2020. Much forerunning activity occurred at what are interpreted to be smaller asperities along the peripheries of the rupture zones of great mainshocks at transform faults and subduction zones. Several great asperities as ascertained from forerunning activity agree with the areas of high seism</span><span style="font-family:Verdana;">ic slip as determined by others using geodetic, mapping of surf</span><span style="font-family:Verdana;">ace faulting, and finite-source seismic modeling. The zones of high slip in many great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities. Asperities are strong, well-coupled portions of plate interfaces. Different patterns of forerunning activity on time scales of up to 45 years are attributed to the sizes and spacing of asperities (or lack of). This permits at least some great asperities along transform faults to be mapped decades before they rupture in great shocks. Rupture zones of many great mainshocks along transform faults are bordered either along strike, at depth or regionally by zones of lower plate coupling including either fault creep</span></span><span style="font-family:""> </span><span style="font-family:Verdana;"> forerunning activity, aftershocks and/or slow-slip events. Forerunning activity to transforms in continental areas is more widespread spatially than that adjacent to oceanic transforms. The parts of the San Andreas fault themselves that ruptured in great California earthquakes during 1812, 1857 and 1906 have been very quiet since 1920;moderate to large shocks have been concentrated on their peripheries. The intraplate shocks studied, however, exhibited few if any forerunning events, which is attributed to the short period of time studied compared to their repeat times. The detection of forerunning and precursory activities for various time scales should be sought on the peripheries of great asperities and not just along the major faults themselves. This paper compliments that on decadal forerunning activity to great and giant earthquakes along subduction zones.
基金the project of " Mechanism for Continental Strong Earthquakes and Their Prediction" , one of the projects in the National Basic Scientific Research and Development Program,grant No.G1998040706.
文摘The Zhangjiakou-Penglai fault zone lies in the northern part of North China Plain and extends along the Zhangjiakou-Huailai-Sanhe-Tianjin-Bohai Sea-Penglai-Yantai-North Huanghai Sea line, it is about 900 km long and some 250-km wide in a northwest direction. The 1679 Sanhe-Pinggu M 8.0 and the 1976 Tangshan M7.8 earthquakes occurred in the fault zone. In this paper an analysis of Gutenberg- Richter’s empirical relation and time process of historic and recent earthquakes along the eastern and western segments of the fault zone separated by the 117°line indicates that they obey a Poison process and, hence, a calculation from it yields a cumulative probability of strong earthquake occurrence along the two segments before 2010, i. e. the probability of M6.0 earthquake occurrence is 0.80 along the eastern segment and the probability of M7. 0 earthquake occurrence is 0.76 along the western segment of the fault zone.
