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Interaction between adjacent left-lateral strike-slip faults and thrust faults: the 1976 Songpan earthquake sequence

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Chinese Science Bulletin 2008年第16期53卷 2520-2526页

作者： Y. john chen Department of Geophysics School of Earth and Space Sciences Peking University

Based on the published focal mechanisms we have built the fault model of the main shocks of the 1976 Songpan earthquake sequence and calculated the coseismic Coulomb stress changes in the region. The results show that most of the aftershocks had occurred in the region where the Coulomb stresses had been increased, indicating a triggering relationship between the main shocks and the aftershocks. We also show that the first main shock (Ms = 7.2), which is a left-lateral slip event, had increased the Coulomb stresses by 5×105 Pa at the second main shock (a thrust event with Ms = 6.7). Therefore, we conclude that the first main shock had triggered the second main shock. The third main shock is also a left-lateral event, however, the triggering relationship between the third main shock and the previous two events is less obvious. General model calculations show that there is a good triggering relation- ship between adjacent left-lateral slip fault and thrust fault, but triggering between parallel slip faults is rather weak.

关键词：松潘大地震序列断层地震波

A new stacking technique in ambient noise tomography

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Earthquake Science 2010年第6期23卷 627-636页

作者： Yongshun john chen Department of Geophysics School of Earth and Space SciencesPeking University

We have developed a new stacking technique in ambient noise tomography to obtain high-quality dispersion curves of Rayleigh waves. This technique is used to stack the vertical components of the Estimated Green Functions （EGFs） obtained respectively from cross correlation of the ambient noise data recorded by a remote seismic station and one of the short distance seismic stations of a seismic array. It is based on a phase-matched filter and is implemented by a four-step iterative process： signal compression, stacking, signal extraction and signal decompression. The iterative process ends and gives the dispersion curve of Rayleigh wave when the predicted one and the processing result converge. We have tested the method using the vertical components of synthetic Rayleigh wave records. Results show that this new stacking method is stable and it can improve the quality of dispersion curves. In addition, we have applied this method to real data. We see that the results given by our new technique are obviously better than the ones employing the traditional method which is a three-step process： signal compression, signal extraction and signal decompression. In conclusion, the new method proposed in this paper can improve the signal to noise ratio of EGFs, and can therefore potentially improve the resolution of ambient noise tomography.

关键词： seismotectonics continental dynamics ambient noise tomography array technique stacking

Long-term seismic network in South China Sea by floating MERMAIDs

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Science China Earth Sciences 2023年第9期66卷 1979-1993页

作者： Yong YU Yongshun john chen Zhen GUO Zengxi GE Department of Ocean Science and Engineering Southern University of Science and TechnologyShenzhen 518055China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China School of Earth and Space Science Peking UniversityBeijing 100871China

Seismic data coverage in ocean regions is sparse,and it is highly challenging to build long-term continuous seismic networks in the oceans due to the restrictions related to the shortage of instruments and great *** lack of data coverage limits effective seismic imaging of deep mantle structures beneath the oceans,which cover 70%of the Earth’s *** newly developed Mobile Earthquake Recorder in Marine Areas by Independent Drivers(MERMAID)can drift with ocean currents at a specified depth while recording seismic *** Southern University of Science and Technology(SUSTech)launched 10 MERMAIDs in the South China Sea(SCS)in May 2021 that formed the South China Sea Floating Seismic Network(SCS-FSN).We analyzed the one-year-long records of the SCS-FSN,identifying 372 cataloged earthquakes and acquiring 1,015 high-quality travel time *** analyzing the records of earthquakes with magnitudes above 7.0 and conducting synthetic waveform calculation,we found that,in addition to the epicentral distance and earthquake magnitude,the earthquake identification ability of the network is also affected by the focal mechanism,sea condition,seafloor relief,and MERMAID working *** the recognition rate of the SCS-FSN is only 16%for earthquakes with magnitudes above 5.5 and epicentral distances less than 90°,this network is expected to collect more than 5,000 high-quality travel time data during its five-year battery *** new data will significantly improve the seismic data coverage,compensating for the lack of long-term continuous seismic network observations in the *** importantly,with this experiment,we are confident that setting up well-designed floating seismic networks in the world’s three oceans could solve the world-class problem of the lack of effective seismic data coverage beneath ocean regions.

关键词： South China Sea MERMAID Floating seismic network Earthquake identification Seismic data coverage

The Hardy-Weinberg principle and its applications in modern population genetics

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Frontiers in Biology 2010年第4期5卷 348-353页

作者： john J.chen Department of Preventive Medicine State University of New York at Stony BrookStony BrookNY 11794-8036USA

The discovery of the Hardy-Weinberg principle marked the beginning of the field of population *** the past hundred years,it has provided a starting point for many population genetic *** this review,the Hardy-Weinberg principle,its statistical testing,and several of its applications in various modern population genetic research areas,including allelic variability and selection in the human leukocyte antigen region,microsatellite genotyping error detection,and accuracy of haplotype estimation,are discussed.

关键词： the Hardy-Weinberg principle statistical testing population genetics human leukocyte antigens microsatellite genotyping haplotype estimation

Toward safer and more efficacious colonoscopy polypectomy

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Laparoscopic, Endoscopic and Robotic Surgery 2022年第1期5卷 10-14页

作者： Zongyu john chen MNGI Digestive Health PAMinneapolisMNUSA AGA Education Committee International Subcommittee BethesdaUSA

Screening and surveillance colonoscopy with removal of precancerous colon polyps has greatly reduced colon cancer morbidity and mortality and has become an important part of China's new strategy for colon cancer *** with polypectomy could lead to complications such as postpolypectomy hemorrhage and incomplete polyp removal contributing to interval colon cancer *** techniques play an important *** evolution of different polypectomy techniques and their advantages and disadvantages have been reviewed to help readers choose and apply the best suitable ones for their individual patient situation toward safer and more efficacious colonoscopy polypectomy.

关键词： Colonoscopy Polypectomy Endoscopic mucosal resection Endoscopic submucosal dissection Endoscopic mucosal stripping

The updated crustal attenuation in North China using M_L amplitude tomography

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Earthquake Science 2010年第6期23卷 541-548页

作者： Shunping Pei Yongshun john chen Key Laboratory of Continental Coil&ion and Plateau Uplift Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China Computational Geodynamics Laboratory Department of Geophysics School of Earth and Space Sciences Peking University Beijing 100871 China

We have updated the lateral variations of the quality factor Q0（Q at 1 Hz） beneath the crust of North China using ML amplitude tomography with near three times *** data were selected from the Annual Bulletin of Chinese Earthquakes（ABCE） in 1985-2009,including 26 283 ML amplitude readings from 4 204 events recorded by 38 *** result is similar with previous research but has higher *** Q0 values are consistent with tectonic and topographic structure in North China.Q0 is low in the active tectonic regions having many faults,such as Bohai bay,North China basin,the Shanxi and Yinchuan grabens,while it is high in the stable Ordos craton.Q0 values are low in several topographically low-lying areas,such as the North China,Taikang-Hefei,and Subei-Huanghai Sea basins,whereas it is high in mountainous and uplift regions exhibiting surface expressions of crystalline basement rocks：the Yinshan,Yanshan,Taihang,Qinling and Dabie mountains,Luxi and Jiaoliao *** factor estimates are also consistent with Pn and Sn velocity *** velocity values in general correspond with high Q0 and vice *** coincides with a common temperature influence in the crust and uppermost mantle.

关键词： amplitude tomography Q value North China

Tomographic structure of East Asia:Ⅱ.Stagnant slab above 660 km discontinuity and its geodynamic implications

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Earthquake Science 2010年第6期23卷 613-626页

作者： Yongshun john chen Shunping Pei Computational Geodynamics Laboratory Department of Geophysics School of Earth and Space Sciences Peking University Beijing 100871 China Key Laboratory of Continental Collision andPlateau Uplift Institute of Tibetan Plateau Research Chinese Aeademy of Sciences Beijing 100085 China

P-wave arrival times of both regional and teleseismic earthquakes were inverted to obtain mantle structures of East Asia. No fast （slab） velocity anomalies was not find beneath the 660-kin discontinuity through tomography besides a stagnant slab within the transition zone. Slow P-wave velocity anomalies are present at depths of 100-250 km below the active volcanic arc and East Asia. The western end of the flat stagnant slab is about 1 500 km west to active trench and may also be correlated with prominent surface topographic break in eastern China. We suggested that active mantle convection might be operating within this horizontally expanded ＂mantle wedge＂ above both the active subducting slabs and the stag- nant flat slabs beneath much of the North China plain. Both the widespread Cenozoic volcanism and associated extensional basins in East Asia could be the manifestation of this vigorous upper mantle convection. Cold or thermal alaomalies associated with the stagnant slabs above the 660-km discontinuity have not only caused a broad depression of the boundary due to its negative Clapeyron slope but also effectively shielded the asthenosphere and continental lithosphere above from any possible influence of mantle plumes in the lower mantle.

关键词： tomography stagnant slab mantle wedge

Tomographic structure of East Asia:*** fast(slab) anomalies beneath 660 km discontinuity

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Earthquake Science 2010年第6期23卷 597-611页

作者： Shunping Pei Yongshun john chen Key Laboratory of Continental Collision and Plateau Uplift Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China Computational Geodynamics Laboratory Department of Geophysics School of Earth and Space Sciences Peking University Beijing 100871 China

This is the first of two papers that describes a regional tomography investigation, which combines P-wave arrival times of both regional and teleseismic earthquakes to obtain 3D mantle structures of East Asia up to 1 000 km depth. The most important findings of this tomography study are reported in this paper as follows. （1） No fast P-wave velocity anomalies can be related to subducted oceanic slabs beneath the 660 km discontinuity; instead the subducted oceanic slabs become flattened and stagnant within the transition zone. （2） The high velocity anomalies in the transition zone extend up to 1 500 km to the westward of the active trenches, which is a unique feature in the worldwide subduetion systems. （3） Slow P-wave velocity anomalies are visible up to -250 km underneath most of the East Asia on the east of 115°E, similar to the area of the stagnant slabs. These observations have important implications for the geodynamic process at depths beneath the East Asia, which might in turn control the widespread Cenozoic volcanism and associated extensional tectonics seen at the Earth＇s surface.

关键词： tomography stagnant slab mantle wedge

Synthetic sensitivity analysis of high frequency radiation of 2011Tohoku-Oki(MW9.0) earthquake

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Earthquake Science 2014年第4期27卷 355-364页

作者： Haoran Meng Yongshun john chen Institute of Theoretical and Applied Geophysics School of Earth and Space Sciences Peking University

Frequency-dependent rupture behavior of sub- duction zone interplate megathrust faults has been observed by back-projection method in different frequency bands （from 0.05 to 5 Hz）. It has been suggested that the down-dip region of the Tohoku megathrust radiated strongly at high frequencies （〉10 Hz） compared with that of the up-dip region. By assuming the same source tirne function of each fault patch, we perform a synthetic sensitivity analysis to compare the energy received from the shallower parts （and further way from the receiver sites） with that frona the deeper parts （and closer to the receiver sites） of the rupture. Our results indicate that regional onshore recordings are probably not adequate to constrain the presence of far-off shore high frequency radiations because of the strong attenuation of this region.

关键词： Tohoku-Oki earthquake - High frequencyradiation Frequency-dependent rupture behavior