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SE5-007
14:20
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14:40
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GROUND MOITON PREDICTION EQUATIONS FOR CRUSTAL EARTHQUAKES IN TAIWAN
Taiwan’s Central Weather Bureau (CWB) has operated a large network of strong-motion instruments since 1992. The enormous number of high-quality digital accelerograms recorded at CWB’s free-field stations has been an invaluable resource to both earthquake engineering practice and earthquake ground-motion research, including the development of ground-motion prediction equation (GMPE). This paper presents our recent research to develop GMPEs for the 5%-damped horizontal pseudo-spectral accelerations of crustal earthquakes in Taiwan, using the CWB ground-motion records and supporting information compiled by Taiwan Power Company’s SHHAC Level-3 probabilistic seismic hazard analysis (PSHA) study. Due to the paucity of recordings of large magnitude (M > 7) earthquakes, how to extrapolate available ground-motion data to the hazard-important domain has been the main challenge of GMPE development in Taiwan. To capture the epistemic uncertainty in extrapolation, we produce a suite of GMPEs by adjusting multiple foreign (non-Taiwan) GMPEs originally developed for shallow crustal earthquakes of other active tectonic regions. These foreign GMPEs are selected because each includes credible magnitude scaling relations of ground motions in the nearfield of large magnitude earthquake. We propose that these scaling relations are applicable in Taiwan to extrapolate collected data to the nearfield of large earthquake. Adjustment to the foreign GMPE is needed mainly to account for the observed regional difference in ground motion amplitude and site effects between Taiwan and the host regions of the foreign GMPEs. Functional form of a few foreign GMPEs is slightly modified to add an effect important to Taiwan data but missing from the original GMPE. GMPE coefficients related to ground-motion scaling in the nearfield of large magnitude are not adjusted, while the rest of GMPE coefficients are adjusted by a crossed mixed-effects regression on the Taiwan data. Residual variance of the adjusted GMPE is decomposed into earthquake, station, and remaining components to provide estimates of residual standard deviation at a single station. The outcome of our study is a set of GMPEs suitable for use in site-specific PHSA to characterize the median and the single-station standard deviation of the predictive distribution of ground motion.
Brian Chiou, Po-Shen Lin
crossed mixed-effect model, ground-motion predictive equation, PSHA, single-station sigma
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SE5-015
14:40
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15:55
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THE STUDY OF LOCAL SOURCE MODEL SETTING TO CONSIDER THE POSSIBLE GEOLOGIC STRUCTURE IN THE OFFSHORE LOCATION
In order to provide environmental energy, wind turbines in the offshore of Taiwan have gradually developed. In addition to wind, and waves, the high seismicity environment is one of the impact factors for wind turbine design in Taiwan. The principal objective of probabilistic seismic hazard analysis (PSHA) of a particular site is to estimate the annual frequency of exceedance of a site subjected to different levels of ground shaking intensity. A feature model of the most seismic source characteristic (SSC) within a range of 320 km around the site should be considered in the PSHA. Although the offshore geologic mapping cannot be developed well until now, nearly studies of the geologic and geophysical investigations interpreted faults within the near offshore zone that are not included in the list of possible faults. In order to consider these possible faults as seismic sources in the areal source zone, the " Virtual Fault" is an aggregate approach to evaluate each interpreted fault within the local offshore areal source zone (PG&E, 2015 ). For the seismic requirement for the wind support structures in the offshore location, this study will model the local areal source zone with virtual faults to consider the probability of possible faults in the hazard calculation. On other hands, the traditional approach is incorporating additional uncertainty in a-value of activity for the areal source zone. The effect for design basis earthquake for the offshore site of the two approaches for areal source zone setting will be discussed in this study.
Yu-Wen Chang, Yu-Chih Huang, Chih-Wei Chang
Areal source zone, offshore, Probabilistic Seismic Hazard Analysis, Virtual Fault
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SE5-004
14:55
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15:15
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TOWARD IMPROVEMENT OF SEISMIC HAZARD ASSESSMENT IN TAIWAN AND RYUKYU ISLANDS
Taiwan and Okinawa prefecture, Japan are located on Ryukyu island-arc with complex plates conjunctions of Philippine sea plate, Pacific plate and Eurasian plate. There are the highest level of seismic activities and destructive earthquakes suffered recently, such as the 1999 Chi-Chi earthquake (Mw7.6) caused 2,400 deaths, and the 2011 Great East Japan earthquake (Mw9.0) claimed 20,000 fatalities. The Ryukyu mega-thrust have large potential to accumulate M 9-class earthquake which will affect Taiwan and Ryukyu (Nansei-shoto) islands. A 3-years cooperative research of Probabilistic Seismic Hazard Assessment (PSHA) was first initialized between China-Korea-Japan after the lesson learned from the 2008 Wenchuan (Mw7.9) earthquake. It then immediately inspired a series of bilateral PSHA interactions of Taiwan-Japan (2012~), NewZealand-Japan (2014~). A series of PSHA workshops of Japan-Taiwan-NewZealand (www.j-shis.bosai.go.jp/intl/tem), and a focus section of SRL (2016) summarized significant progress. The regional seismic activities almost dominate the PSHA result, however, a short history of literary and instrumental capability on earthquakes caused PSHA epistemic uncertainty. Earthquake catalog used in Taiwan PSHA model is for M >= 4.0 since 1973. There is a few information beyond Taiwan margin along a thousand-kilometer length of Ryukyu arc and the Philippine arc. Earthquake catalog used in the Ryukyu islands L-3, Japan PSHA model is for M >= 5.0 since 1983 by considered instrumental detection capability of observation network. To reduce the PSHA epistemic uncertainty due to the lack of densification seismic data, we purpose a Super-Large geotectonic region to mean the annual rate of earthquakes obtained from both of Taiwan and the Ryukyu islands L-3. We are looking forward to work together with Taiwan Earthquake Model to carry on the cooperation research.
Hiroyuki Fujiwara, Ken Xiansheng Hao
Probabilistic Seismic Hazard Assessment, Ryukyu, seismicity, Taiwan
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SE5-005
15:15
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15:35
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PROBABILISTIC SEISMIC HAZARD ASSESSMENT FOR TAIWAN: TEM PSHA2019
Taiwan Earthquake Model (TEM) published the first version of probabilistic seismic hazard assessment for Taiwan (named ‘TEM PSHA2015’) for the ground motion based of engineering bedrock (averaged shear-wave velocity in top 30 meter assumed to be 760 m/sec) with regional and subduction zone seismicity till 2011, and individual single segment fault rupture of the 38 seismogenic structures. Update version to the TEM PSHA2019, we revised the assessment by considering updated fault sources, including the newly identified seismogenic structure with 3D geometry, an up-to-date earthquake catalogue to 2016, state-of-the-art seismic models, and site amplification factors. Parameters of the fault source are updated by the TEM geologists. 3D fault plane geometry is depicted for some structures and possibility of rupture on multiple structures is considered. The earthquake database is recorded by the Central Weather Bureau Seismic Network (CWBSN) from 1973 until 2016. To illustrate seismic activity on fault sources, we incorporated not only a Poisson model, which assumed faults do not memory time-elapse of last rupture, but also the Brownian Passage Time model for those sources with earthquake records. For the crustal seismic hazard that cannot be attributed from a specific fault source, we implemented both area sources and smoothing kernel models into logic tree. In order to better evaluate ground shaking, our assessment includes site amplification factors and corresponding GMPEs. This version of hazard map considers site effect, which could be easily accessed by laymen without science and engineering background.
Ruey-Juin Rau, Yin-Tung Yen, Kuo-Fong Ma, Chung-Han Chan, J. Bruce H. Shyu, Ya-Ting Lee, Yu-Ju Wang
Probabilistic Seismic Hazard Assessment, TEM
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SE5-008
15:35
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15:55
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THE PROJECT SAM: DEVELOPMENT OF PROBABILISTIC SEISMIC GROUND MOTION HAZARD MAP FOR THE ENTIRE PHILIPPINES
The Philippines is located in one of the most seismically hazardous regions of the world and is situated in the vicinity of three (3) major faults namely; the Philippine Trench, formed by the subduction of the western edge of the Philippine Plate under the Eurasia Plate, which is one of the country’s major seismic generators besides the Philippine Fault Zone (PFZ) and the Manila Trench. Many destructive earthquakes have occurred in various parts of the country, of which the most notable and destructive ones were the Mw7.6 Casiguran Aurora Earthquake in August 8, 1968, the Mw8.2 Moro Gulf Earthquake in August 17, 1976, the Mw6.5 Ilocos Norte Earthquake in August 17, 1983, the Mw7.7 North Luzon Earthquake in July 16, 1990, the Mw6.2 Masbate Earthquake in February 15, 2003, the Mw6.9 Negros Oriental Earthquake in February 6, 2012, the Mw7.2 Bohol Earthquake in October 15, 2013, the Mw6.7 Surigao Earthquake in February 10, 2017, the Mw6.5 Leyte Earthquake in July 6, 2017, the Mw6.1 Central Luzon Earthquake in April 22, 2019, and the recent Mw5.5 Surigao del Sur Earthquake in July 13, 2019.One of the key aspects of the proper seismic resistant design and construction of buildings is the proper estimation and documentation of the seismic hazard available to the architect, structural engineers and even to the public. This information should be consistent with the latest developments in seismology and earthquake engineering. The main objective of the project to be carried out is to enhance the Probabilistic Seismic Ground Motion Hazard Maps for the entire Philippines particularly in highly-urbanized regions.
Adam C. Abinales, Carlos M. Villaraza
Earthquake Engineering, ground motion parameters, peak ground acceleration, probabilistic seismic hazard maps, spectral acceleration
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