Since the great 1303 Hongtong, Shanxi, earthquake of magnitude 8, 700 years have elapsed. To analyze the long-term seismic potential, this paper divides the Taiyuan-Linfen portion of the Shanxi graben system into 5 se...Since the great 1303 Hongtong, Shanxi, earthquake of magnitude 8, 700 years have elapsed. To analyze the long-term seismic potential, this paper divides the Taiyuan-Linfen portion of the Shanxi graben system into 5 seismogenic segments. Based on data of historical earthquakes and GPS observation, the authors estimate mean seismic-moment rates and average recurrence intervals of strong earthquakes for the individual segments, and fur-ther analyze relative levels of current stress cumulation on the segments based on mapping b-values along the gra-ben system by using the network seismic data for the recent over 30 years. The main result shows that the Linfen basin segment has an estimated mean seismic-moment rate of 2.211016 Nm/a to 3.031016 Nm/a, and its average recurrence interval for M=7.5 earthquake is estimated to be between 1 560 and 2 140 years. For the Ling-shi-Hongtong segment, the estimated average recurrence interval for M=8 earthquakes is between 4 300 and 5 100 years, equivalent to having a mean moment-rate of 2.581016 Nm/a to 3.101016 Nm/a. The contour map of b-values shows that the two segments of Lingshi-Hongtong and Linfen basin have been being at low or relatively low stress levels, reflecting that since the 1303 M=8 and the 1695 M=7.5 earthquake ruptures, the fault-planes strengths of the both segments have not been resumed yet. And the other two segments, the Houma and the Jiexiu-Fenyang, have relatively high stress levels, and have been already identified as potential risky segments for the coming earthquakes from the analysis combining with the estimated average recurrence intervals of earth-quakes on the both segments.展开更多
Paleoearthquake research represents an essential method for determining recurrence intervals oflarge earthquakes.Reasonable determination of the average recurrence interval and coefficient of variationprovides a cruci...Paleoearthquake research represents an essential method for determining recurrence intervals oflarge earthquakes.Reasonable determination of the average recurrence interval and coefficient of variationprovides a crucial basis for the analysis of the recurrence characteristics of strong earthquakes on intraplatefaults in Chinese mainland.Paleoearthquake data from 145 fault segments of 93 well-studied faults in MainlandChina were collected,organized,and analyzed to discuss the rational estimation of the average recurrenceinterval and coefficient of variation of a strong earthquake occurrence probability model.First,differencesin structural environments were used as a basis to investigate the spatial distribution characteristics of theaverage recurrence intervals of strong earthquakes.The results indicate significant variations in the recurrenceperiods of strong earthquakes in the Sichuan–Yunnan,Xinjiang,North China,and northeastern Qinghai-Tibet Plateau structure zones.The Sichuan–Yunnan structure zone exhibited the shortest average recurrence intervalfor strong earthquakes,which was mainly distributed between 100 and 2000 years,and a relatively high sliprate.The Xinjiang structure zone attained a relatively balanced recurrence interval frequency distribution of1000–4500 years and a moderate slip rate.The North China structure zone showed the lowest slip rate,withthe strong earthquake recurrence interval mainly concentrated between 1000 and 4000 years.The northeastern Qinghai-Tibet Plateau structure zone presented two main frequency peaks in the strong earthquake recurrenceintervals between 1000–3000 years and 3000–5000 years and a relatively high slip rate.The slip rate is a keyfactor influencing the recurrence interval of strong earthquakes,and active faults with high slip rates showshort recurrence intervals.Furthermore,the relationship between fault slip rate,fault type,and the averagerecurrence interval of strong earthquakes was examined.The results indicate a good logarithmic linearrelationship between the fault slip rate and the average recurrence interval of large earthquakes—the higherthe slip rate,the shorter the recurrence interval of strong earthquakes.Fault type also showed a relation to theaverage recurrence interval,with the intervals for various types of active faults gradually increasing in theorder of strike-slip,normal,reverse strike-slip,reverse,and normal strike-slip faults.Second,we calculated theproportions of active faults and various fault types in each structure zone that had a coefficient of variation inrecurrence intervals less than 0.4.The findings reveal that the occurrence of strong earthquakes on most activefaults in Chinese mainland satisfies a quasiperiodic model.The general coefficient of variation across differentstructure zones and fault types ranges between 0.36 and 0.44,which indicates the nonsignificant difference inthe degree of variability in the periodicity of strong earthquake occurrence across various structural zones andfault types.展开更多
文摘Since the great 1303 Hongtong, Shanxi, earthquake of magnitude 8, 700 years have elapsed. To analyze the long-term seismic potential, this paper divides the Taiyuan-Linfen portion of the Shanxi graben system into 5 seismogenic segments. Based on data of historical earthquakes and GPS observation, the authors estimate mean seismic-moment rates and average recurrence intervals of strong earthquakes for the individual segments, and fur-ther analyze relative levels of current stress cumulation on the segments based on mapping b-values along the gra-ben system by using the network seismic data for the recent over 30 years. The main result shows that the Linfen basin segment has an estimated mean seismic-moment rate of 2.211016 Nm/a to 3.031016 Nm/a, and its average recurrence interval for M=7.5 earthquake is estimated to be between 1 560 and 2 140 years. For the Ling-shi-Hongtong segment, the estimated average recurrence interval for M=8 earthquakes is between 4 300 and 5 100 years, equivalent to having a mean moment-rate of 2.581016 Nm/a to 3.101016 Nm/a. The contour map of b-values shows that the two segments of Lingshi-Hongtong and Linfen basin have been being at low or relatively low stress levels, reflecting that since the 1303 M=8 and the 1695 M=7.5 earthquake ruptures, the fault-planes strengths of the both segments have not been resumed yet. And the other two segments, the Houma and the Jiexiu-Fenyang, have relatively high stress levels, and have been already identified as potential risky segments for the coming earthquakes from the analysis combining with the estimated average recurrence intervals of earth-quakes on the both segments.
基金Funded by the National Key Research and Development Program(2022YFC3003502).
文摘Paleoearthquake research represents an essential method for determining recurrence intervals oflarge earthquakes.Reasonable determination of the average recurrence interval and coefficient of variationprovides a crucial basis for the analysis of the recurrence characteristics of strong earthquakes on intraplatefaults in Chinese mainland.Paleoearthquake data from 145 fault segments of 93 well-studied faults in MainlandChina were collected,organized,and analyzed to discuss the rational estimation of the average recurrenceinterval and coefficient of variation of a strong earthquake occurrence probability model.First,differencesin structural environments were used as a basis to investigate the spatial distribution characteristics of theaverage recurrence intervals of strong earthquakes.The results indicate significant variations in the recurrenceperiods of strong earthquakes in the Sichuan–Yunnan,Xinjiang,North China,and northeastern Qinghai-Tibet Plateau structure zones.The Sichuan–Yunnan structure zone exhibited the shortest average recurrence intervalfor strong earthquakes,which was mainly distributed between 100 and 2000 years,and a relatively high sliprate.The Xinjiang structure zone attained a relatively balanced recurrence interval frequency distribution of1000–4500 years and a moderate slip rate.The North China structure zone showed the lowest slip rate,withthe strong earthquake recurrence interval mainly concentrated between 1000 and 4000 years.The northeastern Qinghai-Tibet Plateau structure zone presented two main frequency peaks in the strong earthquake recurrenceintervals between 1000–3000 years and 3000–5000 years and a relatively high slip rate.The slip rate is a keyfactor influencing the recurrence interval of strong earthquakes,and active faults with high slip rates showshort recurrence intervals.Furthermore,the relationship between fault slip rate,fault type,and the averagerecurrence interval of strong earthquakes was examined.The results indicate a good logarithmic linearrelationship between the fault slip rate and the average recurrence interval of large earthquakes—the higherthe slip rate,the shorter the recurrence interval of strong earthquakes.Fault type also showed a relation to theaverage recurrence interval,with the intervals for various types of active faults gradually increasing in theorder of strike-slip,normal,reverse strike-slip,reverse,and normal strike-slip faults.Second,we calculated theproportions of active faults and various fault types in each structure zone that had a coefficient of variation inrecurrence intervals less than 0.4.The findings reveal that the occurrence of strong earthquakes on most activefaults in Chinese mainland satisfies a quasiperiodic model.The general coefficient of variation across differentstructure zones and fault types ranges between 0.36 and 0.44,which indicates the nonsignificant difference inthe degree of variability in the periodicity of strong earthquake occurrence across various structural zones andfault types.
