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D0-013
16:10
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16:25
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STRONG GROUND MOTION APPLICATION IN NCREE AFTER CHI-CHI, TAIWAN EARTHQUAKE
1999 Chi-Chi Taiwan earthquake was a most disaster earthquake in recent decades that was also a significant watershed moment for engineering seismology development in Taiwan. Formerly, there were lack of seismic observation data and limited application to engineering purpose in Taiwan before Chi-Chi earthquake. Such as it’s lack of detailed site information for TSMIP (Taiwan Strong Motion Instrumental Program) stations, lack of connection for rapid ground motion observation and simulation to engineering application, limited understanding to strong ground motion characteristics of huge disaster earthquakes and long period shaking during large earthquakes. Owing to lack of strong ground motion observation, large amount foreign data were used to application of assesmetic design instead of local ones. In NCREE (National Center for Research on Earthquake Engineering, Taiwan), application of strong ground motion to engineering purpose was an important input for seismic design especially large amount strong motion records were collected since Chi-Chi earthquake. In this study, application of strong ground motion in NCREE recent years will be introduced, including three important fields who will be inputs for design earthquake for building structures that were ground motion characteristics, probabilistic seismic hazard analysis (PSHA) and near fault effect. Ground motion characteristic could be subdivided to site database for TSMIP, shallow velocity models for strong motion stations, localized development of high frequency ground motion simulation technique, rapid ground motion observation for earthquake early warning purpose etc. Meanwhile, for PSHA progress, micro-zonation of design earthquake and next generation ground motion prediction equation for Taiwan was constructed. Finally, near fault pulse-like motions were collected in the world to check near field effect for strong ground motions.
Kuo-Liang Wen
ground motion characteristics, Ground Motion Prediction Equation, logic tree, probability seismic hazard analysis, single station sigma, Taiwan
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SE5-017
16:25
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16:40
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ANALYSIS OF SEISMIC HAZARD POTENTIAL IN TAIPEI AREA RELATIVE TO SITE EFFECT
The island of Taiwan lies at the boundary between the Philippine Sea plate and the Eurasia plate. Accordingly, the majority of seismic energy release near Taiwan originates from the two subduction zones. It is therefore not surprising that Taipei has repeatedly been struck by large earthquakes. Analysis of seismic hazard potential becomes necessary in Taipei Area for the Central Geological Survey announced the Sanchiao active fault as Category II. In this study, a catalog of more than 2000 shallow earthquakes occurred from 1900 to 2018 with Mw magnitudes ranging from 5.0 to 8.2, and 11 disastrous earthquakes occurred from 1683-1899, as well as Sanchiao active fault in the vicinity are used to estimate the seismic hazard potential in Taipei Area. Furthermore, the probabilities of seismic intensity exceeding CWB intensity 5, 6, 7 and MMI VI, VII, VIII in 10, 30, and 50-year periods in above areas are also analyzed in this study. In addition, significantly pattern with higher earthquake hazard potential relative to site effect of seismic station TAP056 in Taipei Area also compared. Results of this study will show which areas with higher earthquake hazard potential in Taipei Area. They provide a valuable database for the seismic design of critical facilities. It will help mitigate Taipei Area earthquake disaster loss in the future, as well as provide critical information for emergency response plans.
Kun-Sung Liu
Disaster Prevention and Relief, Sanchiao fault, Seismic Hazard Potential, Site Effect, Taipei Area
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SE5-013
16:40
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16:55
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The Influence of Fault Slip Rate Uncertainty on Earthquake Probability Estimation- A Case Study in Northern Taiwan
Recurrence intervals and earthquake probabilities in northern Taiwan were derived using geological slip rates and geodetic slip deficit rates for understanding the influence of fault slip rate uncertainty for earthquake probability estimation. Taking the Hsinchu fault as an example, the lower bound of long-term slip rate is 1.9 mm/yr, and the calculated recurrence interval is 567 years, while the lower bound of geodetic slip deficit rate is 0.3 mm/yr, and the calculated recurrence interval is 3594 years. Although the difference of these two slip rates is only 1.6 mm/yr, the recurrence interval difference is approximately 6 times. On the other hand, the upper bound of geological slip rate is 3.5 mm/yr, and the calculated recurrence interval is 308 years, while the upper bound of geodetic slip deficit rate is 2.8 mm/yr, and the calculated recurrence interval is 385 years. The difference of recurrence intervals is not significant. In this case, we understand that a minor difference to lower bound of the slip rate may result in a significant difference to the upper bound of recurrence interval (the influence of the multiple). For the Hsincheng fault, the derived 30-years earthquake probability is 3.2% using the BPT model according to the long-term slip rate of 1.8-2.5 mm/yr, while the calculated 30-years probability is 5.5% based on the geodetic slip deficit rate of 0.5-3.7 mm/yr. The minor difference shows that if the mean geological and geodetic slip rates are similar, the range of upper and lower bounds has little effect on the probability calculation. In addition, the recurrence interval of 98 years on Shitan fault was inferred using a geodetic slip deficit rate of 11.1 mm/yr. However, no large-scale earthquake has occurred since the 1935 Hsinchu-Taichung earthquake. The recurrence interval of the Sanyi fault calculated from the geodetic slip deficit rate of 12.4 mm/yr is 122 years. However, no large-scale earthquake occurred since 1900 A.D. on the Sanyi fault, either. Although the upper bound of slip deficit rates on these two faults could be reduced to match the actual observations, the significant uncertainty on geodetic slip deficit rates caused by the poor resolution of geodetic data may not be excluded. Finally, the calculated probabilities from the geodetic slip deficit rate are higher than that of geological data by more than 10% for the Shihtan fault, the Sanyi fault, and the Tuntzuchiao fault. The long-term slip rates of the three faults are all evaluated from the topographic scarps, which may imply that the slip rate estimated by topographic scarp is underestimated. In addition, the tectonic structure of these three fault zones is complicated so that the slip rate on the three faults may be overestimated. Obviously, it is necessary to clear up the significance and uncertainty when we consider the slip rate from various sources in the probability assessment in a future disaster earthquake. To further clarify this problem, a dense geodetic network across faults is recommended to estimate more reliable slip deficit rates. In addition, if the height difference of formation across the fault could be found by drilling data, it may provide a more accurate slip rate for evaluation.
Yi-Jui Lee, Yin-Tung Yen, Kuo-En Ching, Wu-Lung Chang, Ray Y. Chuang
earthquake probability, geological slip rate, recurrence interval, slip deficit rate
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SE5-014
16:55
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17:10
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A SITE DATABASE FOR TAIWAN STRONG MOTION NETWORK
Site effect is usually treated as a simple site parameter like Vs30, which is a value of average shear wave velocity for the top 30 m of layers, in Ground Motion Prediction Equations (GMPEs). Although debates on usage of Vs30 for its advantage and disadvantage are still an open question, it has become the most widely be used site parameter in ground motion prediction, seismic hazard analysis, and building codes. In order to make up for the insufficient of Vs30 especially in regions covered by large thickness of sediments, depth to the horizons with shear wave velocity of larger than 1.0 km/s (or 1.5 km/s, 2.5 km/s), the so called Z1.0 (or Z1.5, Z2.5), was recently introduced to the GMPEs of the Next Generation of Attenuation Equations (NGA) projects. Dominant frequency of HVSR is considered corresponding to a certain velocity interface that would be critical for site effect. The high-frequency attenuation factor, i.e. kappa, is considered a significant parameter controlling attenuation of high-frequency seismic waves. High correlation is believed between kappa and local site conditions. S-wave velocity profiles of the Engineering Geology Database for TSMIP (EGDT) were measured using suspension PS-logging at more than 450 strong ground motion stations throughout Taiwan. Accurate Vs30 is therefore provided by the site database. In addition, two estimated Vs30 models were tested and included for those stations without velocity logging. Although the depths of most stations were only 35 m, Z1.0 still can be derived at dozens of stations near basin edges, piedmont, and mountains. Several techniques including microtremor array, receiver function, and microtremor HVSR inversion have been used to obtain S-wave velocity profiles at strong motion stations and thus the parameter Z1.0 can be derived. A relationship between Vs30 and Z1.0 for Taiwan is consequently evaluated and further compared with those for Japan and California.
Chun-Hsiang Kuo, Che-Min Lin, Shun-Chiang Chang, Kuo-Liang Wen
Kappa, Vs30, Z1.0
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SE5-011
17:10
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17:25
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OBSERVED PULSE-LIKED GROUND MOTION AND RUPTURE DIRECTIVITY EFFECT IN TAIWAN GROUND MOTION DATASET
In this study, we analyzed around 40000 available 3-axes ground motion records in Taiwan ground motion database by using pulse indicator, and up to 200 records have been identified as pulse-liked ground motion with horizontal or vertical velocity pulses. We also analyzed the record-specific residual of each record from around 300 events in Taiwan ground motion database, and significant rupture directivity effect can be observed in several earthquakes e.g. 2010 JiaXian Earthquake, 2013 NanTou Earthquake and 2016 Mei-Nong Earthquake. Unlike the observations from the residual analysis of NGA-West 2 Project database, we found that the rupture directivity influences on the ground motion intensity not only for long period but also for short period spectral acceleration. We showed that involving rupture directivity model in current ground motion model can improve the ground motion prediction accuracy significantly especially for the earthquakes with strong rupture directivity effect. We also found that around 70% pulse-like ground motion records occurred within 55 degree of the rupture directivity direction in azimuth, and it benefits the occurrence prediction of the pulse-like ground motion for future earthquakes. Methodology about how to consider the impact of the rupture directivity effect and the near-fault pulse-liked ground motion on the ground motion intensity will be proposed based on the observations in this study.
Shu-Hsien Chao, Chun-Hsiang Kuo, Hsin-Hua Huang, Chiao-Chu Hsu, Jyh-Cherng Jan
Ground Motion Prediction Equation, Probabilistic Seismic Hazard Analysis, Pulse Liked Ground Motion, Rupture directivity effect
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SE5-012
17:25
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17:40
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APPLYING H/V FOURIER SPECTRAL RATIOS FOR PREDICTING THE SITE EFFECT OF GROUND MOTION
In the past, many studies have illustrated that the horizontal-to-vertical (H/V) Fourier spectral ratios evaluated from ambient vibration data or strong motion data can be used to represent the site amplification characteristics of a target site. However, most of current available GMPEs only used average shear wave velocity over to 30m layers (Vs30) and depth to shear-wave velocity up to 1 km/s (Z1.0) as predictor variables to quantify the site effect. In this study, we evaluate H/V Fourier spectral ratios of each strong motion station in Taiwan by using the ground motion records of earthquakes. Then two predictor variables derived from H/V Fourier spectral ratios are proposed to quantify the site amplification with and without available Vs30 and Z1.0 information. Comparing to using Vs30 and Z1.0 as predictors, the standard deviation of station-to-station variability in the developed GMPE can be reduced about 5% for each period of spectral acceleration while supplementing two additional predictor variables derived from H/V Fourier spectral ratios. While Vs30 and Z1.0 information are not available for a target site, the site amplification can also be predicted by using the proposed two predictors from H/V Fourier spectral ratios with as similar accuracy as using Vs30 and Z1.0. The accuracy of the ground motion prediction can be improved for a target site with available information of H/V Fourier spectral ratios, and it benefits the future work of conducting site-specific probability seismic hazard analysis for the target site without available Vs30 and Z1.0 information.
Shu-Hsien Chao, Che-Min Lin, Chun-Hsiang Kuo, Jyun-Yan Huang
Ground Motion Prediction Equation, H/V Fourier Spectral Ratio, Site Effect
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