With the recent development of digital Micro Electro Mechanical System （MEMS） sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record...With the recent development of digital Micro Electro Mechanical System （MEMS） sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a seismic event depends upon the efficiency of triggering algorithm, apart from the sensor＇s sensitivity. There are several classic triggering algorithms developed to detect seismic events, ranging from basic amplitude threshold to more sophisticated pattern recognition. Algorithms based on STA/LTA are reported to be computationally efficient for real time monitoring. In this paper, we analyzed several STA/LTA algorithms to check their efficiency and suitability using data obtained from the Quake Catcher Network （network of MEMS accelerometer stations）. We found that most of the STA/LTA algorithms are suitable for use with MEMS accelerometer data to accurately detect seismic events. However, the efficiency of any particular algorithm is found to be dependent on the parameter set used （i.e., window width of STA, LTA and threshold level）.展开更多
Major cases of the Ms8.0 Wenchuan earthquake are obtained through field investigations of the epicenter and high-intensity areas, and the relationships among earthquake faults, ground motion and earthquake disasters n...Major cases of the Ms8.0 Wenchuan earthquake are obtained through field investigations of the epicenter and high-intensity areas, and the relationships among earthquake faults, ground motion and earthquake disasters near fault zones are analyzed. Both strong deformation and ground rupture lead to significant damages of the buildings, indicating that it is necessary to keep safe distance away from active faults and to take other necessary measures. There are two reasons for that the buildings near the surface rupture zones have withstood in the strong earthquake, other than their seismic resistance capacities, with the first being the site condition, and the second the reduced effective stress and low rupture velocity. The forms of structural damages are complex in the fault areas, with shear failure and tensile and compressive damages. Those structures in urban areas that have used qualified materials and followed the building codes performed well in the earthquake. Survey results also indicate that structures of flexible materials may show better seismic performance.展开更多
The Wenchuan earthquake of 12 May 2008 is the most destructive earthquake in China in the past 30 years in terms of property damage and human losses. In order to understand the earthquake process and the geo-morpholog...The Wenchuan earthquake of 12 May 2008 is the most destructive earthquake in China in the past 30 years in terms of property damage and human losses. In order to understand the earthquake process and the geo-morphological factors affecting the seismic hazard, we simulated the strong ground mo-tion caused by the earthquake, incorporating three-dimensional (3D) earth structure, finite-fault rupture, and realistic surface topography. The simulated ground motions reveal that the fault rupture and basin structure control the overall pattern of the peak ground shaking. Large peak ground velocity (PGV) is distributed in two narrow areas: one with the largest PGV values is above the hanging wall of the fault and attributed to the locations of fault asperities and rupture directivity; the other is along the north-western margin of the Sichuan Basin and caused by both the directivity of fault rupture and the ampli-fication in the thick sediment basin. Rough topography above the rupture fault causes wave scattering, resulting in significantly larger peak ground motion on the apex of topographic relief than in the valley. Topography and scattering also reduce the wave energy in the forward direction of fault rupture but increase the PGV in other parts of the basin. These results suggest the need for a localized hazard as-sessment in places of rough topography that takes the topographic effects into account. Finally, had the earthquake started at the northeast end of the fault zone and ruptured to the southwest, Chengdu would have suffered a much stronger shaking than it experienced on 12 May, 2008.展开更多
基金IIT Roorkee under the Faculty Initiation Grant No.100556
文摘With the recent development of digital Micro Electro Mechanical System （MEMS） sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a seismic event depends upon the efficiency of triggering algorithm, apart from the sensor＇s sensitivity. There are several classic triggering algorithms developed to detect seismic events, ranging from basic amplitude threshold to more sophisticated pattern recognition. Algorithms based on STA/LTA are reported to be computationally efficient for real time monitoring. In this paper, we analyzed several STA/LTA algorithms to check their efficiency and suitability using data obtained from the Quake Catcher Network （network of MEMS accelerometer stations）. We found that most of the STA/LTA algorithms are suitable for use with MEMS accelerometer data to accurately detect seismic events. However, the efficiency of any particular algorithm is found to be dependent on the parameter set used （i.e., window width of STA, LTA and threshold level）.
基金supported by National Natural Science Foundation of China (No. 40674016 and No. 50478060)the Seismic Industry Foundation of Ministry of Science and Technology of China ([2007]203/8-53)
文摘Major cases of the Ms8.0 Wenchuan earthquake are obtained through field investigations of the epicenter and high-intensity areas, and the relationships among earthquake faults, ground motion and earthquake disasters near fault zones are analyzed. Both strong deformation and ground rupture lead to significant damages of the buildings, indicating that it is necessary to keep safe distance away from active faults and to take other necessary measures. There are two reasons for that the buildings near the surface rupture zones have withstood in the strong earthquake, other than their seismic resistance capacities, with the first being the site condition, and the second the reduced effective stress and low rupture velocity. The forms of structural damages are complex in the fault areas, with shear failure and tensile and compressive damages. Those structures in urban areas that have used qualified materials and followed the building codes performed well in the earthquake. Survey results also indicate that structures of flexible materials may show better seismic performance.
基金the U.S. National Science Foundation (Grant Nos. EAR 0738779 and OCE 0727919)the National Basic Research Program of China (Grant No. 2004CB418404)partially by the National Nature Science Foundation of China (Grant No. 40521002)
文摘The Wenchuan earthquake of 12 May 2008 is the most destructive earthquake in China in the past 30 years in terms of property damage and human losses. In order to understand the earthquake process and the geo-morphological factors affecting the seismic hazard, we simulated the strong ground mo-tion caused by the earthquake, incorporating three-dimensional (3D) earth structure, finite-fault rupture, and realistic surface topography. The simulated ground motions reveal that the fault rupture and basin structure control the overall pattern of the peak ground shaking. Large peak ground velocity (PGV) is distributed in two narrow areas: one with the largest PGV values is above the hanging wall of the fault and attributed to the locations of fault asperities and rupture directivity; the other is along the north-western margin of the Sichuan Basin and caused by both the directivity of fault rupture and the ampli-fication in the thick sediment basin. Rough topography above the rupture fault causes wave scattering, resulting in significantly larger peak ground motion on the apex of topographic relief than in the valley. Topography and scattering also reduce the wave energy in the forward direction of fault rupture but increase the PGV in other parts of the basin. These results suggest the need for a localized hazard as-sessment in places of rough topography that takes the topographic effects into account. Finally, had the earthquake started at the northeast end of the fault zone and ruptured to the southwest, Chengdu would have suffered a much stronger shaking than it experienced on 12 May, 2008.
