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Science China Earth Sciences 2006年第3期49卷 272-282页

作者： zhou shiyong CHEN Xiaofei Department of Geophysics Peking University Beijing 100871 China Department of Geophysics Peking University Beijing 100871 China

The new inversion algorithm developed based on the recent progress in thenonlinear programming study by us is used to invert the earthquake source process of Chi Chiearthquake M_w7.6, 20 Semptember,1999, Taiwan. A curve fault model is constructed in our inversionto make the fault model close to the real rupturing fault to reduce the influence from thediscrepancy between the constructed fault model and the real rupturing fault. The results show that(1) the rupture process of the Chi Chi earthquake source lasted about 32 seconds and the mainfaulting occurred between 6th to 21st second after the start of the ruptures and the high slip areawere mainly located at the northern segment of the fault. (2) The slip was dominated by thrustfaulting. The average rake angle was 64.5°, which was very consistent with those inverted by USGS,Harvard and CWB (Central Weather Bureau of Taiwan). The amount of the moment inverted in this paperwas 7.76x10^(20) NM, which was a slightly bigger than those inverted by USGS and Harvard. (3) Aclear nucleation step existed in the source faulting process and it lasted about 6 seconds. Themoment release rate accelerated obviously at the end of the nucleation step. The faulting startedfrom the southern segment and mainly occurred at the northern segment after 10 seconds. At the endof this paper, we analyzed the reliability of the inversion result via comparing with the GPSobservations and discussed its scientific signification.

关键词： Chi Chi earthquake, source rupture process, waveform inversion, near-source data, source mechanism.

Application and discussion of statistical seismology in probabilistic seismic hazard assessment studies

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Science China Earth Sciences 2022年第2期65卷 257-268页

作者： Weilai PEI shiyong zhou Jiancang ZHUANG Ziyao XIONG Jian PIAO School of Earth and Space Sciences Peking UniversityBeijing 100871China The Institute of Statistical Mathematics Research Organization of Information and SystemsTokyo 1908562Japan

Earthquakes are one of the natural disasters that pose a major threat to human lives and property. Earthquake prediction propels the construction and development of modern seismology;however, current deterministic earthquake prediction is limited by numerous difficulties. Identifying the temporal and spatial statistical characteristics of earthquake occurrences and constructing earthquake risk statistical prediction models have become significant;particularly for evaluating earthquake risks and addressing seismic planning requirements such as the design of cities and lifeline projects based on the obtained insight. Since the 21 st century, the occurrence of a series of strong earthquakes represented by the Wenchuan M8 earthquake in 2008 in certain low-risk prediction areas has caused seismologists to reflect on traditional seismic hazard assessment globally. This article briefly reviews the development of statistical seismology, emphatically analyzes the research results and existing problems of statistical seismology in seismic hazard assessment, and discusses the direction of its development. The analysis shows that the seismic hazard assessment based on modern earthquake catalogues in most regions should be effective. Particularly, the application of seismic hazard assessment based on ETAS(epidemic type aftershock sequence)should be the easiest and most effective method for the compilation of seismic hazard maps in large urban agglomeration areas and low seismic hazard areas with thick sedimentary zones.

关键词： Statistical seismology Earthquake prediction Probabilistic seismic hazard assessment Stress release model Epidemic type aftershock sequence model

Induced earthquakes in the development of unconventional energy resources

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Science China Earth Sciences 2017年第9期60卷 1632-1644页

作者： YANG HongFeng LIU YaJing WEI Meng ZHUANG JianCang zhou shiyong Earth System Science Programme Faculty of Science Chinese University of Hong Kong Hong Kong 999077 China Earth and Planetary Sciences McGill UniversityMontreal Quebec H3A 2A7 Canada Graduate School of Oceanography University of Rhode lsland Narragansett Rhode lsland 02882 USA Institute of Statistical Mathematics Tokyo 190-8562 Japan ITAG Institute of Theoretical and Applied Geophysics Peking University Beijing 100871 China

It has long been known that human activities such as waste fluid disposal and reservoir impoundment may cause earthquakes. Recently, anthropogenic activities to tackle the increasing energy demand and to address climate change issues are also reported to induce earthquakes. These activities have a common attribute in that fluids are injected and extracted underground and induce spatiotemporal changes of pore pressure and stress, which may cause slip on faults. Induced earthquakes not only pose significant impacts on seismic hazard assessment and preparation, but also raise the question to the society as how to balance the economic needs of resources development and the public's concerns about potential environmental impacts. Here we review the observations of fluid-injection/extraction induced earthquakes, ground deformation associated with these activities, and their physical mechanisms. Furthermore, we discuss the influences of induced earthquakes on seismic hazard models, regulatory policies on these anthropogenic activities, and current development of academic, industrial and government initiatives and collaborations in order to understand this intriguing phenomenon and address associated challenges.

关键词： Induced earthquake Fluid injection Energy demand Climate change

The spatiotemporal variation of the b-value and its tectonic implications in North China

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Earthquake Science 2014年第3期27卷 301-310页

作者： Yujie Zheng shiyong zhou School of Earth and Space Sciences Peking University

In this study, we adopt an improved Bayesian approach based on free-knot B-spline bases to study the spatial and temporal distribution of the b-value. Synthetic tests show that the improved Bayesian approach has a superior performance compared to the Bayesian approach as well as the widely used maximum likelihood estimation （MLE） method in fitting the real variation of b-values. We then apply the improved Bayesian approach to North China and find that the b-value has a clear relevance to seismicity. Temporal changes of b-values are also investigated in two specific areas of North China. We interpret sharp decreases in the b-values as useful messages in earthquake hazard analysis.

关键词： Improved Bayesian approach B-splines b-value Frequency-magnitude distribution North China Earthquake hazard analysis

A test on methods for MC estimation based on earthquake catalog

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Earth and Planetary Physics 2018年第2期2卷 150-162页

作者： YiJian zhou shiyong zhou JianCang Zhuang Department of Geophysics Peking UniversityBeijing 100871China Institute of Statistical Mathematics 10-3 Midoori-ChoTachikawaTokyo190-8569Japan

This study tested five methods widely used in estimating the complete magnitudes(M_C) of earthquake catalogs. Using catalogs of observed earthquake properties, we test the performance of these five algorithms under several challenging conditions, such as small volume of events and spatial-temporal heterogeneity, in order to see whether the algorithms are stable and in agreement with known data. We find that the maximum curvature method(MAXC) has perfect stability, but will significantly underestimate M_C unless heterogeneity is absent. M_C estimated by the b-value stability method(MBS) requires many events to reach a stable result. Results from the goodness of fit method(GFT) were unstable when heterogeneity lowered the fitness level. The entire magnitude range method(EMR) is relatively stable in most conditions, and can reflect the change in M_C when heterogeneity exists, but when the incomplete part of the earthquake catalog is dismissed, this method fails. The median-based analysis of the segment slope method(MBASS) can tolerate small sample size, but is incapable of reflecting the missing degree of small events in aftershock sequences. In conditions where M_C changes rapidly, such as in aftershock sequences, observing the time sequence directly can give a precise estimation of the complete sub-catalog, but only when the number of events available for study is large enough can the MAXC, GFT, and MBS methods give a similarly reliable estimation.

关键词： complete magnitude of an earthquake catalog G-R law b-value FMD

Inferring seismic hazard in Sichuan-Yunnan region of China based on the modern earthquake catalogue (1980-2019)

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Earthquake Science 2020年第3期33卷 107-115页

作者： Ziyao Xiong shiyong zhou Jiancang Zhuang School of Earth and Space Sciences Peking UniversityBeijing100871China The Institute of Statistical Mathematics Tokyo 1908562Japan

Based on the modern earthquake catalogue,the incomplete centroidal voronoi tessellation(ICVT)method was used in this study to estimate the seismic hazard in Sichuan-Yunnan region of *** calculated spatial distributions of the total seismic hazard and background seismic hazard in this *** Bayesian delaunay tessellation smoothing method put forward by Ogata was used to calculate the spatial distributions of *** results show that seismic hazards in Sichuan-Yunan region are high,and areas with relatively high hazard values are distributed along the main faults,while seismic hazards in Sichuan basin are relatively low.

关键词： seismic hazard analysis Voronoi tessellation spatial smoothing b-value

Discussion on 'Was the 2008 Wenchuan earthquake triggered by Zipingpu Reservoir?'

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Earthquake Science 2010年第6期23卷 577-581页

作者： shiyong zhou Kai Deng Cuiping Zhao Wanzheng Cheng School of Earth and Space Sciences Peking University Beijing 100871 China Institute of Earthquake Science China Earthquake Administration Beijing 100036 China Earthquake Administration of Sichuan Province Chengdu 610041 China

Some recent publications presented a result suggesting that Zipingpu reservoir hastened the occurrence of the 2008 Ms8.0 Wenchuan earthquake by tens to hundreds of years. Their researches calculated the Coulomb stress change induced by Zipingpu reservoir on the rupturing fault of Wenchuan earthquake. Their results, however, are critically dependent upon the 3-D event location, reservoir location, and the fault plane orientation. We repeated Ge et al.＇s work in this paper and found that an improper dip angle parameter of their 2-D fault model might lead to a wrong conclusion. Both the modeling results based on the 2-D model and 3-D model with proper fault parameters will show Coulomb stress changes alone were neither large enough nor had the correct orientation to affect the occurrence of Wenchuan earthquake, which supports our recent argument based on the local seismicity analysis and the induced Coulomb stress change calculation with a 3-D model.

关键词： Wenchuan earthquake reservoir induced seismicity Coulomb stress

Doppler effect of the rupture process of the great M_W7.9 Wenchuan earthquake

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Earthquake Science 2010年第6期23卷 535-539页

作者： Ge Jin Youcai Tang shiyong zhou Yongshun John Chen Institute of Theoretical and Applied Geophysics (ITA G) School of Earth and Space Sciences Peking University Beijing 100871 China Lamont-Doherty Earth Observatory Columbia University in the New York City Palisades NY 10964 USA

In this study we performed a classical spectrum analysis of seismic waveforms recorded at far field stations of the great MW7.9 Wenchuan earthquake to observe the shifts of the corner frequency with azimuth due to the Doppler *** results show that this damaging great earthquake had a dominating rupture propagation direction of 64.0°.The equivalent radius of the fault rupture surface was estimated to be 33 km,yielding the rupture area of about 3 500 *** the length of the rupture fault surface is about 230 km if the depth（or width） extent is 15 *** computer program developed in this study can quickly provide the information about the source of a future large（damaging） earthquake,which could be very useful for predicting aftershocks and planning the rescue operations.

关键词： Doppler effect rupture process Wenchuan earthquake corner frequency unidirectional

A high-resolution seismic catalog for the 2021 M_(S)6.4/M_(W)6.1 Yangbi earthquake sequence, Yunnan, China: Application of AI picker and matched filter

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Earthquake Science 2021年第5期34卷 390-398页

作者： Yijian zhou Abhijit Ghosh Lihua Fang Han Yue shiyong zhou Youjin Su Institute of Geophysics China Earthquake AdministrationBeijing 100081China Department of Earth Sciences University of CaliforniaRiversideCalifornia 92521USA Institute of Theoretical and Applied Geophysics Peking UniversityBeijing 100871China Yunnan Earthquake Agency Yunnan 650224China

We present a high-resolution seismic catalog for the 2021 M_(S)6.4/M_(W)6.1 Yangbi *** catalog has a time range of 2021-05-01 to 2021-05-28,and contains~8,000 well located *** captures the features of the whole foreshock sequence and the early *** designed a detection strategy incorporating both an artificial intelligent(AI)picker and a matched filter ***,we adopt a hybrid AI method incorporating convolutional and recurrent neural network(CNN&RNN)for event detection and phase picking respectively(***),a light-weight AI picker that can be trained with small volume of *** is first trained with detections from a STA/LTA and Kurtosis-based method called PAL,and then construct a rather complete template set of~4,000 ***,the matched filter algorithm MESS augments the initial detections and measures differential travel times with cross-correlation,which finally results in precise *** process gives 9,026 detections,among which 7,943 events can be well *** catalog shows as expected power-law distribution of frequency magnitude and reveals detailed pattern of seismicity *** main features are:(1)the foreshock sequence images simple fault geometry with consistent strike,but also show a variable event depth along strike;(2)the mainshock ruptures the same fault of the foreshock sequence and activate conjugate faults further to the southeast;(3)complex seismicity are developed in the post-seismic period,indicating complex triggering ***,our catalog provides a reliable basis for further investigations,such as b-value studies,rupture process,and triggering relations.

关键词： Yangbi earthquake seismic catalog earthquake detection AI picker matched filter.

Distribution of the low velocity bulk in the middle-to-lower crust of southern Tibet: implications for formation of the north–south trending rift zones

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Earthquake Science 2014年第2期27卷 149-157页

作者： Mingming Jiang Yinshuang Ai shiyong zhou Yongshun John Chen Key Laboratory of the Earth’s Deep Interior Institute of Geology and GeophysicsChinese Academy of Sciences Institute of Theoretical and Applied Geophysics School of Earth and Space SciencesPeking University

We conducted the ambient noise tomography to image the shallow crustal structure of southern Tibet. The2D maps of phase velocity anomalies at the periods of10–16 s show that the low velocities are mainly confined along or near some of the rift zones. While the maps at the periods of 18–25 s show that the coherent patterns that the low velocities expand outside of the rift zones. It means that the low velocities are prevailing in the middle crust of southern Tibet. According to the previous study of surface wave tomography with teleseismic data,we find that the low velocities from the lower crust to the lithospheric mantle are also restricted to the same rift zones. Thus,the integrated knowledge of the distribution of the low velocities in southern Tibet provides some new insight on the formation of the north–south trending rift zones. Compiling the multidiscipline evidences,we conclude that the rifting was an integrated process of the entire lithosphere in the early stage（＊26–10 Ma）,but mainly occurred within the upper crust due to the weakening a decoupling in the low velocity middle crust in the late stage（later than ＊8 Ma）.

关键词： Ambient noise tomography Southern Tibet North–south trending rift zones