Source rupture of the 2008 Wenchuan earthquake were estimated based on backward projection of seismic waves to its source plane. Observations from regional seismic arrays and near source stations were employed to stud...Source rupture of the 2008 Wenchuan earthquake were estimated based on backward projection of seismic waves to its source plane. Observations from regional seismic arrays and near source stations were employed to study the rupture behavior in its different spatial and temporal stages. Regional broadband arrays from Taiwan and northern Vietnam were used to determine the overall rupture processes of this earthquake. With high density of station distribution of both seismic arrays, the rupture processes of this earthquake were determined. Seismic energy determined from array waveforms have been back-projected to the rupture plane of earthquake to determine its slip distributions in fault plane. The rupture processes have been reconstructed based on time-dependent imaged seismic energy radiated from earthquake fault plane. Analyzed results of this study indicated that the 2008 Wenchuan earthquake has rupture duration more than 80 seconds with major asperities radiated its energy on several seconds after the earthquake rupture initiation. The radiated seismic energy showed complex spatial distribution on the fault plane. The rupture initiated at its epicenter and extended to its northeast direction about 250 km. The averaged rupture velocity of this earthquake is determined to be near 3.3 km/s. According to near source records, the first large amplitude arrivals were delayed by seconds with respect to the origin time and were preceded by a small-scale slip. Based on a beamforming analysis, some near source recordings were used in this study to investigate the initial rupture process of this event. We will discuss the rupture behavior in multiple scales using both near fault and regional arrays for source images in its different stages.展开更多
The disastrous Wenchuan, Sichuan, earthquake (MS=8.0) on 12 May 2009 ruptured several major thrust faults of the Longmenshan fold-and-thrust belt, along the western margin of the Sichuan Basin. This earthquake produce...The disastrous Wenchuan, Sichuan, earthquake (MS=8.0) on 12 May 2009 ruptured several major thrust faults of the Longmenshan fold-and-thrust belt, along the western margin of the Sichuan Basin. This earthquake produced significant damages of the area, with more than 60,000 of casualties and countless economic losses, and was one of the largest natural disasters ever occurred in the Sichuan Province in history. The earthquake was accompanied by several surface ruptures, including the central rupture (Beichuan fault), the frontal rupture (Pengguan fault), and a shorter Xiaoyudong rupture between the central and frontal ruptures. The frontal rupture, which is part of the Pengguan fault, had predominantly thrust offset. The total length of the frontal rupture is up to 90 km, with a maximum vertical offset between 3 and 4 m. Although it is called the frontal rupture, the structure is not the frontal fault of the system. South of Hanwang Town, the Pengguan fault follows a mountain front-parallel valley, whereas the actual mountain front structure did not rupture during this earthquake. Immediately north of Hanwang Town, on the other hand, the mountain front approximately follows the fault, but the rupture terminated not very far to the north. Uplifted alluvial surfaces, however, indicate that there is still a blind frontal thrust underneath the western margin of the basin. Along the Jing River, widespread and continuous river terraces provide the opportunity to characterize the late Quaternary slip rates of the faults. Furthermore, unique drainage patterns south of the Xiaoyudong rupture suggest that the area behaves distinctively, and the Xiaoyudong rupture may be an independent fault with previous rupture events.展开更多
文摘Source rupture of the 2008 Wenchuan earthquake were estimated based on backward projection of seismic waves to its source plane. Observations from regional seismic arrays and near source stations were employed to study the rupture behavior in its different spatial and temporal stages. Regional broadband arrays from Taiwan and northern Vietnam were used to determine the overall rupture processes of this earthquake. With high density of station distribution of both seismic arrays, the rupture processes of this earthquake were determined. Seismic energy determined from array waveforms have been back-projected to the rupture plane of earthquake to determine its slip distributions in fault plane. The rupture processes have been reconstructed based on time-dependent imaged seismic energy radiated from earthquake fault plane. Analyzed results of this study indicated that the 2008 Wenchuan earthquake has rupture duration more than 80 seconds with major asperities radiated its energy on several seconds after the earthquake rupture initiation. The radiated seismic energy showed complex spatial distribution on the fault plane. The rupture initiated at its epicenter and extended to its northeast direction about 250 km. The averaged rupture velocity of this earthquake is determined to be near 3.3 km/s. According to near source records, the first large amplitude arrivals were delayed by seconds with respect to the origin time and were preceded by a small-scale slip. Based on a beamforming analysis, some near source recordings were used in this study to investigate the initial rupture process of this event. We will discuss the rupture behavior in multiple scales using both near fault and regional arrays for source images in its different stages.
文摘The disastrous Wenchuan, Sichuan, earthquake (MS=8.0) on 12 May 2009 ruptured several major thrust faults of the Longmenshan fold-and-thrust belt, along the western margin of the Sichuan Basin. This earthquake produced significant damages of the area, with more than 60,000 of casualties and countless economic losses, and was one of the largest natural disasters ever occurred in the Sichuan Province in history. The earthquake was accompanied by several surface ruptures, including the central rupture (Beichuan fault), the frontal rupture (Pengguan fault), and a shorter Xiaoyudong rupture between the central and frontal ruptures. The frontal rupture, which is part of the Pengguan fault, had predominantly thrust offset. The total length of the frontal rupture is up to 90 km, with a maximum vertical offset between 3 and 4 m. Although it is called the frontal rupture, the structure is not the frontal fault of the system. South of Hanwang Town, the Pengguan fault follows a mountain front-parallel valley, whereas the actual mountain front structure did not rupture during this earthquake. Immediately north of Hanwang Town, on the other hand, the mountain front approximately follows the fault, but the rupture terminated not very far to the north. Uplifted alluvial surfaces, however, indicate that there is still a blind frontal thrust underneath the western margin of the basin. Along the Jing River, widespread and continuous river terraces provide the opportunity to characterize the late Quaternary slip rates of the faults. Furthermore, unique drainage patterns south of the Xiaoyudong rupture suggest that the area behaves distinctively, and the Xiaoyudong rupture may be an independent fault with previous rupture events.
