Field-based Quantification of Empirical Relationships Between Pore-pressure Change and Seismic Shaking Using Data from the Chi-Chi (Mw = 7.6) Earthquake, Taiwan

使用台湾 Chi-Chi (Mw = 7.6) 地震数据对孔隙压力变化与地震振动之间的经验关系进行现场量化

• 批准号: 0125548
• 负责人: Chi-Yuen Wang
• 金额: $ 9.47万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2004-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0125548&HistoricalAwards=false
• 关键词: Field; based; Quantification; Empirical; Relationships

Alluvial fans over the world are often shaken by large earthquakes that have led to some of the worst historical landslides even on very gentle slopes (e.g., the Turnagain Heights landslide, Anchorage, Alaska, in the 1964 Alaskan earthquake). However, systematic field evidence for coseismic change in pore-pressure in alluvial fans was not available until after the 1999 Chi-Chi, Taiwan, earthquake. The 1999 Chi-Chi (Mw=7.6) earthquake in central Taiwan was recorded by a dense network of modern seismological, geodetic and hydrologic instruments. Widespread coseismic pore-pressure changes, captured for the first time by 188 hydrologic wells in a network of 70 hydrologic stations, occurred across a large alluvial fan (the Choshui River fan) west of the epicenter of the earthquake. Ground-motion on this fan, both during the main-shock and during several large (M 6) aftershocks of the Chi-Chi earthquake was recorded by 80 broadband strong-motion accelerometers at high sampling rate, and the data was promptly published. A complex, yet systematic, pattern in the coseismic change in pore-pressure emerged from the digitized water-level records that led to a hypothesis that the coseismic pore-pressure change was due to the nonlinear mechanical response of sediments to seismic shaking. The hypothesis, however, was based on an empirical relationship from a small number of laboratory experiments performed on small samples under applied stresses with magnitude and frequency greatly different from that during earthquake shaking. The availability of both the ground-motion data and the hydrological data from the Chi-Chi earthquake has created a rare opportunity for a quantitative field test of the laboratory-based relationship between the pore-pressure change in sediments and seismic shaking. This project combines both the hydrological data and the seismological data from the Chi-Chi earthquake in a search of the empirical relationship between the two data sets that would be the first field-based relationship between pore-pressure change and seismic shaking, and would greatly facilitate our understanding and assessment of liquefaction and landslide potential in alluvial fans during earthquakes, and would thus be of great value to the seismic engineering community.

世界各地的冲积扇经常受到大地震的震动，这些地震导致了一些历史上最严重的山体滑坡，即使是在非常平缓的斜坡上（例如，1964年阿拉斯加地震中阿拉斯加安克雷奇的Turnagain高地滑坡）。然而，直到1999年台湾集集地震后，才有系统的现场证据表明冲积扇中的孔隙压力发生了同震变化。1999年台湾中部集集地震（Mw=7.6）由现代地震，大地测量和水文仪器的密集网络记录。广泛的同震孔隙压力的变化，捕获的第一次由188个水文威尔斯在网络的70个水文站，发生在一个大冲积扇（浊水溪扇）的震中以西。在集集地震主震和几次6级大余震期间，该扇上的地面运动被80个宽带强震加速度计以高采样率记录下来，并且数据被及时公布。一个复杂的，但系统的，模式出现在同震孔隙压力变化的数字化水位记录，导致一个假设，同震孔隙压力的变化是由于非线性的机械响应的沉积物地震震动。然而，这一假设是基于一个经验关系，从少量的实验室实验中进行的小样本下施加的应力的幅度和频率大大不同，在地震震动。集集地震的地面运动数据和水文数据的可用性创造了一个难得的机会，定量的现场测试的实验室为基础的沉积物中的孔隙压力变化和地震震动之间的关系。本计画结合集集地震的水文资料与地震资料，以探讨两组资料间的经验关系，这将是第一个以现场为基础的孔隙压力变化与地震震动间的关系，并将大大有助于我们了解与评估地震期间冲积扇液化与山崩的可能性，因此对地震工程界具有很大的价值。