Probabilistic seismic hazard assessmentsfor Southeast Asia: Innovation, application, and prospection
詹忠翰 博士
Earth Observatory of Singapore, Nanyang Technological University, Singapore
2019.10.24 （星期四）13:30-15:00，理科二号楼2821
Abstract：
Although most countries in northern Southeast Asia have seismic hazard maps, these national products reveal a widerange of methodologies and quality. Thus, my colleagues and I have conducted a uniform assessment acrossthe region through standardized approach, databases, and regional hazard maps. To apply this assessment to Southeast Asia requires a uniform set of databases that incorporates both earthquake catalogues and fault parameters. The earthquake database contains seismic parameters obtained from global andnational seismic networks, harmonized by removal of duplicate events and theuse of moment magnitude. The fault database includes fault parameters from previous studies and the databases implemented for national hazard maps. Another crucial input for seismic hazard assessment is proper evaluation of ground-shaking attenuation through ground-motion prediction equation (GMPE). Since few GMPEs have been proposed using local observations from this region, attenuationbehaviours are evaluated by comparison of instrumental observations and feltintensities for recent earthquakes with predicted ground shaking from published GMPEs.
Utilizing our databases and the best-fitting GMPEs, I have constructed regional probabilistic seismic hazard maps. The assessment shows highest seismic hazard levels near those faults with high slip rates. In addition, this assessment demonstrates the important fact that regions with low earthquake probability may have a higher aggregate probability of future earthquakes, since they encompass much larger areas than the areas of high probability. The significant irony then is that in areas of low to moderate probability, where building codes usually provide less seismic resilience, seismic risk is likely to be greater. The outcomes not only contribute to national seismic hazard mitigation plan, help Bagan successfully inscribedas a UNESCO World Heritage Site, but also support for the Natural Catastrophe Data and Analytics Exchange (NatCatDAX) and the ASEAN Disaster Risk Financing and Insurance Phase 2 (ADRFI-2).
In the future, the seismic hazard assessment will incorporate a dynamic seismic model using the discrete element method that simulates plates-tectonic movements. The anticipated outcome of this approach will provide not only better constraints on PSHA but also better understanding on tectonic evolution. I will also explore innovations in modelling ground motion attenuation through simulating waveforms to satisfy with the requirements for engineering purposes.
Bio：
    Dr. Chan was trained in seismology and gained a PhD degree from National Central University, Taiwan. In his early career in the GFZ German Research Centre for Geosciences, Germany, and National Taiwan University, Taiwan, he studied in seismicity activity, earthquake forecasting, seismic hazard assessments, and development of seismic risk assessments. Now he is working at Earth Observatory of Singapore, Nanyang Technological University, Singapore. Based on his background, he is involving some scientific and applied topics, including earthquake physics, seismicity forecasting, innovating new seismic hazard approaches based on international and national projects. Although his work experience has mainly been in research institutions, he is able to connect pure science with practical applications, having participated in several applied projects. Through his experience running training courses for scientists and engineers, invited speeches at different research organizations, and media interviews, he has become proficient atdelivering presentations to the general public, as well as professional researchers.
Discrete element modeling of a subductionzone with a seafloor irregularity and its impact on the seismic cycle
焦利青 博士
Institut de Physiquedu Globe de Paris (IPGP), France
2019.10.24 （星期四）13:30-15:00，理科二号楼2821
Abstract：
Seafloor irregularities such as seamounts, ridges, or basins influence rupture behavior along the subducting slab and in the overriding plate, thus affecting earthquake cycles. Whether seafloor irregularities increase the likelihood of large earthquakes in a subduction zone remains contested, partially due to a narrow focus either on fault network developmentor on rupture pattern. Here, using the discrete element method (DEM), we simulate a subducting slab with a seafloor irregularity and the resulting deformation pattern of the overriding plate, which comprises the fault network development and the associated rupture pattern. Our results show the rupture along three main regions: megathrust, splay and backtrust fault regions and the rupture length various from tens to more than one hundred kilometers. The ruptures distribute along the slab and faults in the overriding plate, since the irregularity could accumulate the stress. The modeled recurrence interval of large events and the lengths of the ruptures are overall comparable to that from the paleoseismic record.  Our results show the coseismic slip decreases and interseismic slip increases from the surface downwards. We conclude that the presence of seafloor irregularities significantly affect rupture events along the slab and fault patterns in the overriding plate. Our results thus contribute to seismic and tsunami hazard assessments in subduction zones.
Bio:
    Liqing Jiao received her PhD in Tectonics in 2016 from the Earth Observatory of Singapore (EOS), Nanyang TechnologicalUniversity (NTU). There, she worked under Prof. Paul Tapponnier on discreteelement modeling (DEM) of large-scale continental deformation and silicic volcanic eruptions. After graduation, she worked with Prof. Tapponnier for twomore years on the DEM modeling of faulting in subduction zones and the irregularity impact on the seismic cycle. She also simulated the coseismic rupture of the 2018 Palu earthquake, and compared the modeling results with the observations. Currently, Liqing is a postdoctoral research fellow at the Institut de Physique du Globe de Paris (IPGP), France. She is working with Prof. Yann Klinger in the Lithosphere Tectonics and Mechanics group, and focuses on the co-seismically continental strike-slip faulting in Mongolia.