The M=7.6 Jiji (Chi-Chi) earthquake, Taiwan Province, on September 21, 1999 (local time) is a thrust fault style earthquake. The empirical attenuation relations of the horizontal and vertical peak ground accelerations...The M=7.6 Jiji (Chi-Chi) earthquake, Taiwan Province, on September 21, 1999 (local time) is a thrust fault style earthquake. The empirical attenuation relations of the horizontal and vertical peak ground accelerations (PGA) for the Jiji (Chi-Chi) earthquake are developed by regression method. By examining the residuals from the Jiji (Chi-Chi) earthquake-specific peak acceleration attenuation relations, it is found that there are systematic differences between PGA on the hanging-wall and footwall. The recorded peak accelerations are higher on the hanging-wall and lower on the footwall. The clear asymmetry of PGA distribution to the surface rupture trace can also be seen from the PGA contour map. These evidences indicate that the PGA attenuates faster on the hanging-wall than on the footwall. In the study of near-source strong motion, seismic hazard assessment, scenario earthquake and seismic disaster prediction, the style-of-faulting must be considered in order that the attenuation model can reflect the characteristic of ground motion in various seismic environmental regions.展开更多
A large earthquake (Mw=7.6) occurred in Jiji (Chi-Chi), Taiwan, China on September 20, 1999, and was followed by many moderate-size shocks in the following days. Two of the largest aftershocks with the magnitudes of M...A large earthquake (Mw=7.6) occurred in Jiji (Chi-Chi), Taiwan, China on September 20, 1999, and was followed by many moderate-size shocks in the following days. Two of the largest aftershocks with the magnitudes of Mw=6.1 and Mw=6.2, respectively, were used as empirical Green's functions (EGFs) to obtain the source time functions (STFs) of the main shock from long-period waveform data of the Global Digital Seismograph Network (GDSN) including IRIS, GEOSCOPE and CDSN. For the Mw=6.1 aftershock of September 22, there were 97 pairs of phases clear enough from 78 recordings of 26 stations; for the Mw=6.2 aftershock of September 25, there were 81 pairs of phases clear enough from 72 recordings of 24 stations. For each station, 2 types of STFs were retrieved, which are called P-STF and S-STF due to being from P and S phases, respectively. Totally, 178 STF individuals were obtained for source-process analysis of the main shock. It was noticed that, in general, STFs from most of the stations had similarities except that those in special azimuths looked different or odd due to the mechanism difference between the main shock and the aftershocks; and in detail, the shapes of the STFs varied with azimuth. Both of them reflected the stability and reliability of the retrieved STFs. The comprehensive analysis of those STFs suggested that this event consisted of two sub-events, the total duration time was about 26 s, and on the average, the second event was about 7 s later than the first one, and the moment-rate amplitude of the first event was about 15% larger than that of the second one.展开更多
The September 21, 1999, Jiji （Chi-Chi） Mw7.6 earthquake is the strongest event occurred since 1900 in Taiwan of China. It is located in the middle segment of the western seismic zone of Taiwan. Based on several vers...The September 21, 1999, Jiji （Chi-Chi） Mw7.6 earthquake is the strongest event occurred since 1900 in Taiwan of China. It is located in the middle segment of the western seismic zone of Taiwan. Based on several versions of China earthquake catalogue this study found that a seismic gap of M≥5 earthquakes appeared, in and around the epicenter region, 24 years before and lasted up to the mainshock occurrence. This study also noticed that there existed a lager seismically quiet region of M≥4 earthquakes, which lasted for about 2.5 years before the mainshock occurrence, The spatial variation pattern of regional seismicity before the mainshock seems to match with its coseismic source rupture process. The mentioned seismicity gap and seismic quiescence might be an indication of the preparation process of the Jiji strong earthquake.展开更多
This paper investigates long-period ground motion characteristic of the 1999 Jiji （Chi-Chi）, Taiwan, mainshock and aftershocks on the basis of lots of high quality digital strong motion records. The study attaches t...This paper investigates long-period ground motion characteristic of the 1999 Jiji （Chi-Chi）, Taiwan, mainshock and aftershocks on the basis of lots of high quality digital strong motion records. The study attaches the importance to the variation of strength of the long-period ground motion with the magnitude, distance, and site condition. In the meantime, the near-fault long-period ground motion characteristic is analyzed. The result shows that the shape of the long-period response spectrum is mainly controlled by site condition and magnitude （the spectrum of class D＋E is wider than that of class B＋C, and the spectrum of larger magnitude is wider than that of smaller magni- tude）, and the effect of fault distance on the shape is not evident. And near-fault long-period ground motion characteristic depends on fault activity apparently, that is to say, the long-term ground motion in the hanger is stronger than that in the footwall, and the long-term ground motion in the north is stronger than that in the south.展开更多
基金National Key Basic Research Project (G1998040700).
文摘The M=7.6 Jiji (Chi-Chi) earthquake, Taiwan Province, on September 21, 1999 (local time) is a thrust fault style earthquake. The empirical attenuation relations of the horizontal and vertical peak ground accelerations (PGA) for the Jiji (Chi-Chi) earthquake are developed by regression method. By examining the residuals from the Jiji (Chi-Chi) earthquake-specific peak acceleration attenuation relations, it is found that there are systematic differences between PGA on the hanging-wall and footwall. The recorded peak accelerations are higher on the hanging-wall and lower on the footwall. The clear asymmetry of PGA distribution to the surface rupture trace can also be seen from the PGA contour map. These evidences indicate that the PGA attenuates faster on the hanging-wall than on the footwall. In the study of near-source strong motion, seismic hazard assessment, scenario earthquake and seismic disaster prediction, the style-of-faulting must be considered in order that the attenuation model can reflect the characteristic of ground motion in various seismic environmental regions.
基金State Natural Science Foundation of China (49904004) and IPGP of France.Contribution No. 02FE2007, Institute of Geophysics, Ch
文摘A large earthquake (Mw=7.6) occurred in Jiji (Chi-Chi), Taiwan, China on September 20, 1999, and was followed by many moderate-size shocks in the following days. Two of the largest aftershocks with the magnitudes of Mw=6.1 and Mw=6.2, respectively, were used as empirical Green's functions (EGFs) to obtain the source time functions (STFs) of the main shock from long-period waveform data of the Global Digital Seismograph Network (GDSN) including IRIS, GEOSCOPE and CDSN. For the Mw=6.1 aftershock of September 22, there were 97 pairs of phases clear enough from 78 recordings of 26 stations; for the Mw=6.2 aftershock of September 25, there were 81 pairs of phases clear enough from 72 recordings of 24 stations. For each station, 2 types of STFs were retrieved, which are called P-STF and S-STF due to being from P and S phases, respectively. Totally, 178 STF individuals were obtained for source-process analysis of the main shock. It was noticed that, in general, STFs from most of the stations had similarities except that those in special azimuths looked different or odd due to the mechanism difference between the main shock and the aftershocks; and in detail, the shapes of the STFs varied with azimuth. Both of them reflected the stability and reliability of the retrieved STFs. The comprehensive analysis of those STFs suggested that this event consisted of two sub-events, the total duration time was about 26 s, and on the average, the second event was about 7 s later than the first one, and the moment-rate amplitude of the first event was about 15% larger than that of the second one.
文摘The September 21, 1999, Jiji （Chi-Chi） Mw7.6 earthquake is the strongest event occurred since 1900 in Taiwan of China. It is located in the middle segment of the western seismic zone of Taiwan. Based on several versions of China earthquake catalogue this study found that a seismic gap of M≥5 earthquakes appeared, in and around the epicenter region, 24 years before and lasted up to the mainshock occurrence. This study also noticed that there existed a lager seismically quiet region of M≥4 earthquakes, which lasted for about 2.5 years before the mainshock occurrence, The spatial variation pattern of regional seismicity before the mainshock seems to match with its coseismic source rupture process. The mentioned seismicity gap and seismic quiescence might be an indication of the preparation process of the Jiji strong earthquake.
基金National Natural Science Foundation of China (50278090).
文摘This paper investigates long-period ground motion characteristic of the 1999 Jiji （Chi-Chi）, Taiwan, mainshock and aftershocks on the basis of lots of high quality digital strong motion records. The study attaches the importance to the variation of strength of the long-period ground motion with the magnitude, distance, and site condition. In the meantime, the near-fault long-period ground motion characteristic is analyzed. The result shows that the shape of the long-period response spectrum is mainly controlled by site condition and magnitude （the spectrum of class D＋E is wider than that of class B＋C, and the spectrum of larger magnitude is wider than that of smaller magni- tude）, and the effect of fault distance on the shape is not evident. And near-fault long-period ground motion characteristic depends on fault activity apparently, that is to say, the long-term ground motion in the hanger is stronger than that in the footwall, and the long-term ground motion in the north is stronger than that in the south.
