Wanpeng Feng - Academia.edu (original) (raw)

Papers by Wanpeng Feng

Journal of Geophysical Research, 2011

By combining observations from satellite radar, body wave seismology and optical imagery, we have... more By combining observations from satellite radar, body wave seismology and optical imagery, we have determined the fault segmentation and sequence of ruptures for the 2010 Mw 6.8 Yushu (China) earthquake. We have mapped the fault trace using displacements from SAR image matching, interferometric phase and coherence, and 2.5 m SPOT-5 satellite images. Modeling the event as an elastic dislocation with three segments fitted to the fault trace suggests that the southeast and northwest segments are near vertical, with the central segment dipping 70° to the southwest; slip occurs mainly in the upper 10 km, with a maximum slip of 1.5 m at a depth of 4 km on the southeastern segment. The maximum slip in the top 1 km (i.e., near surface) is up to 1.2 m, and inferred locations of significant surface rupture are consistent with displacements from SAR image matching and field observations. The radar interferograms show rupture over a distance of almost 80 km, much larger than initial seismological and field estimates of the length of the fault. Part of this difference can be attributed to slip on the northwestern segment of the fault being due to an Mw 6.1 aftershock two hours after the main event. The remaining difference can be explained by a non-uniform slip distribution with much of the moment release occurring at depths of less than 10 km. The rupture on the central and southeastern segments of the fault in the main shock propagated at a speed of 2.5 km/s southeastward toward the town of Yushu located at the end of this segment, accounting for the considerable building damage. Strain accumulation since the last earthquake on the fault segment beyond Yushu is equivalent to an Mw 6.5 earthquake.

Geochemistry Geophysics Geosystems, 2008

1] The 1998 M w 5.7 Zhangbei-Shangyi (China) earthquake is the largest to have occurred in northe... more 1] The 1998 M w 5.7 Zhangbei-Shangyi (China) earthquake is the largest to have occurred in northern China since the large 1976 M s 7.8 Tangshan earthquake. Due to its proximity to Beijing, the capital of China, it has therefore gained a lot of attention. A great number of studies have been conducted using seismic and geodetic data, but few are able to identify conclusively the orientation of the primary fault plane for this earthquake. In this paper, two independent ERS synthetic aperture radar interferograms are used to determine precisely the location and magnitude of coseismic surface displacements ($11 cm in the radar line of sight). Modeling the event as dislocation in an elastic half-space suggests that the earthquake is associated with a buried shallow NNE-SSW oriented thrust fault with a limited amount of lateral displacement, which is consistent with seismic intensity distribution and aftershock locations.

Journal of Applied Geodesy, 2009

With its global coverage and all-weather imaging capability, Interferometric SAR (InSAR) has been... more With its global coverage and all-weather imaging capability, Interferometric SAR (InSAR) has been revolutionizing our ability to image the Earth's surface and the evolution of its shape over time. In turn, this has led to many new insights into geophysical and engineering processes, such as volcanoes, earthquakes, landslides and mining activity. In this study, we used an advanced InSAR time series technique to map ground motion of an area in Northern Tibet using ENVISAT images acquired between 2003 and 2007. In order to minimise the e¤ects of baseline decorrelation, a subset of possible pairs having a perpendicular baseline (i.e. orbital separation) of less than 400 m was chosen for the InSAR time series analysis. The time series results reveal an 'unexpected' nonlinear ground motion: the area of interest was relatively stable during the period from 2003 to the middle of 2004, whilst it has exhibited a nearly linear uplift of about 8 cm since the middle of 2004. Examination of high-resolution ALOS PRISM images shows that the uplift signal occurred over the Huatugou oil field and is most likely caused by water injection. This study highlights the potential of In-SAR as an early detection tool of surface deformations.

Science in China Series D: Earth Sciences, 2009

Focal mechanism and dynamic rupture process of the Wenchaun M s8.0 earthquake in Sichuan province... more Focal mechanism and dynamic rupture process of the Wenchaun M s8.0 earthquake in Sichuan province on 12 May 2008 were obtained by inverting long period seismic data from the Global Seismic Network (GSN), and characteristics of the co-seismic displacement field near the fault were quantitatively analyzed based on the inverted results to investigate the mechanism causing disaster. A finite fault model with given focal mechanism and vertical components of the long period P-waves from 21 stations with evenly azimuthal coverage were adopted in the inversion. From the inverted results as well as aftershock distribution, the causative fault of the great Wenchuan earthquake was confirmed to be a fault of strike 225°/dip 39°/rake 120°, indicating that the earthquake was mainly a thrust event with right-lateral strike-slip component. The released scalar seismic moment was estimated to be about 9.4×1020-2.0×1021 Nm, yielding moment magnitude of M w7.9–8.1. The great Wenchuan earthquake occurred on a fault more than 300 km long, and had a complicated rupture process of about 90 s duration time. The slip distribution was highly inhomogeneous with the average slip of about 2.4 m. Four slip-patches broke the ground surface. Two of them were underneath the regions of Wenchuan-Yingxiu and Beichuan, respectively, with the first being around the hypocenter (rupture initiation point), where the largest slip was about 7.3 m, and the second being underneath Beichuan and extending to Pingwu, where the largest slip was about 5.6 m. The other two slip-patches had smaller sizes, one having the maximum slip of 1.8 m and lying underneath the north of Kangding, and the other having the maximum slip of 0.7 m and lying underneath the northeast of Qingchuan. Average and maximum stress drops over the whole fault plane were estimated to be 18 MPa and 53 MPa, respectively. In addition, the co-seismic displacement field near the fault was analyzed. The results indicate that the features of the co-seismic displacement field were coincident with those of the intensity distribution in the meizoseismal area, implying that the large-scale, large-amplitude and surface-broken thrust dislocation should be responsible for the serious disaster in the near fault area.

Science in China Series D: Earth Sciences, 2009

The moment tensor solution, source time function and spatial-temporal rupture process of the M s6... more The moment tensor solution, source time function and spatial-temporal rupture process of the M s6.4 earthquake, which occurred in Ning’er, Yunnan Province, are obtained by inverting the broadband waveform data of 20 global stations. The inverted result shows that the scalar seismic moment is 5.51×1018 Nm, which corresponds to a moment magnitude of M W 6.4. The correspondent best double couple solution results in two nodal planes of strike 152°/dip 54°/rake 166°, and strike 250°/dip 79°/ rake 37°, respectively. Considering the isoseismals and geological structures in the meizoseismal region, the first nodal plane (strike 152°/ dip 54°/ rake 166°) is preferred to be the seismogenic fault. Thus, the M s6.4 earthquake occurred mainly along a right-lateral fault striking 152°. The source time function shows that the duration time of the earthquake is about 14 s. The most of the energy releases within the first 11 s and in 11–14 s the rupture is weak. The snapshots of the slip-rate indicate that the rupture process has 3 more detailed stages. In the first stage of the first 4 s after rupture initiation, the rupture propagates simultaneously toward both strike and dip directions; in the second stage of the following 3 s, the rupture extends to down-dip direction; and in the third stage, the rupture looks to be scattering on the fault. In general, this earthquake is of bilateral rupture, and the rupture mainly takes place in strike-dip direction. The major ruptured area is in the shape of a diamond with a dimension of 19 km. On the whole fault plane, the maximum slip is about 1.2 m, the average slip is about 0.1 m, the maximum slip-rate is 0.4 m/s and the average slip-rate is 0.1 m/s. The features of the co-seismic theoretical displacement field of the Ning’er earthquake fault, calculated based on the inverted fault parameters, are consistent with those of the observed isoseismals.

Journal of Geophysical Research, 2011

By combining observations from satellite radar, body wave seismology and optical imagery, we have... more By combining observations from satellite radar, body wave seismology and optical imagery, we have determined the fault segmentation and sequence of ruptures for the 2010 Mw 6.8 Yushu (China) earthquake. We have mapped the fault trace using displacements from SAR image matching, interferometric phase and coherence, and 2.5 m SPOT-5 satellite images. Modeling the event as an elastic dislocation with three segments fitted to the fault trace suggests that the southeast and northwest segments are near vertical, with the central segment dipping 70° to the southwest; slip occurs mainly in the upper 10 km, with a maximum slip of 1.5 m at a depth of 4 km on the southeastern segment. The maximum slip in the top 1 km (i.e., near surface) is up to 1.2 m, and inferred locations of significant surface rupture are consistent with displacements from SAR image matching and field observations. The radar interferograms show rupture over a distance of almost 80 km, much larger than initial seismological and field estimates of the length of the fault. Part of this difference can be attributed to slip on the northwestern segment of the fault being due to an Mw 6.1 aftershock two hours after the main event. The remaining difference can be explained by a non-uniform slip distribution with much of the moment release occurring at depths of less than 10 km. The rupture on the central and southeastern segments of the fault in the main shock propagated at a speed of 2.5 km/s southeastward toward the town of Yushu located at the end of this segment, accounting for the considerable building damage. Strain accumulation since the last earthquake on the fault segment beyond Yushu is equivalent to an Mw 6.5 earthquake.

Geochemistry Geophysics Geosystems, 2008

1] The 1998 M w 5.7 Zhangbei-Shangyi (China) earthquake is the largest to have occurred in northe... more 1] The 1998 M w 5.7 Zhangbei-Shangyi (China) earthquake is the largest to have occurred in northern China since the large 1976 M s 7.8 Tangshan earthquake. Due to its proximity to Beijing, the capital of China, it has therefore gained a lot of attention. A great number of studies have been conducted using seismic and geodetic data, but few are able to identify conclusively the orientation of the primary fault plane for this earthquake. In this paper, two independent ERS synthetic aperture radar interferograms are used to determine precisely the location and magnitude of coseismic surface displacements ($11 cm in the radar line of sight). Modeling the event as dislocation in an elastic half-space suggests that the earthquake is associated with a buried shallow NNE-SSW oriented thrust fault with a limited amount of lateral displacement, which is consistent with seismic intensity distribution and aftershock locations.

Journal of Applied Geodesy, 2009

With its global coverage and all-weather imaging capability, Interferometric SAR (InSAR) has been... more With its global coverage and all-weather imaging capability, Interferometric SAR (InSAR) has been revolutionizing our ability to image the Earth's surface and the evolution of its shape over time. In turn, this has led to many new insights into geophysical and engineering processes, such as volcanoes, earthquakes, landslides and mining activity. In this study, we used an advanced InSAR time series technique to map ground motion of an area in Northern Tibet using ENVISAT images acquired between 2003 and 2007. In order to minimise the e¤ects of baseline decorrelation, a subset of possible pairs having a perpendicular baseline (i.e. orbital separation) of less than 400 m was chosen for the InSAR time series analysis. The time series results reveal an 'unexpected' nonlinear ground motion: the area of interest was relatively stable during the period from 2003 to the middle of 2004, whilst it has exhibited a nearly linear uplift of about 8 cm since the middle of 2004. Examination of high-resolution ALOS PRISM images shows that the uplift signal occurred over the Huatugou oil field and is most likely caused by water injection. This study highlights the potential of In-SAR as an early detection tool of surface deformations.

Science in China Series D: Earth Sciences, 2009

Focal mechanism and dynamic rupture process of the Wenchaun M s8.0 earthquake in Sichuan province... more Focal mechanism and dynamic rupture process of the Wenchaun M s8.0 earthquake in Sichuan province on 12 May 2008 were obtained by inverting long period seismic data from the Global Seismic Network (GSN), and characteristics of the co-seismic displacement field near the fault were quantitatively analyzed based on the inverted results to investigate the mechanism causing disaster. A finite fault model with given focal mechanism and vertical components of the long period P-waves from 21 stations with evenly azimuthal coverage were adopted in the inversion. From the inverted results as well as aftershock distribution, the causative fault of the great Wenchuan earthquake was confirmed to be a fault of strike 225°/dip 39°/rake 120°, indicating that the earthquake was mainly a thrust event with right-lateral strike-slip component. The released scalar seismic moment was estimated to be about 9.4×1020-2.0×1021 Nm, yielding moment magnitude of M w7.9–8.1. The great Wenchuan earthquake occurred on a fault more than 300 km long, and had a complicated rupture process of about 90 s duration time. The slip distribution was highly inhomogeneous with the average slip of about 2.4 m. Four slip-patches broke the ground surface. Two of them were underneath the regions of Wenchuan-Yingxiu and Beichuan, respectively, with the first being around the hypocenter (rupture initiation point), where the largest slip was about 7.3 m, and the second being underneath Beichuan and extending to Pingwu, where the largest slip was about 5.6 m. The other two slip-patches had smaller sizes, one having the maximum slip of 1.8 m and lying underneath the north of Kangding, and the other having the maximum slip of 0.7 m and lying underneath the northeast of Qingchuan. Average and maximum stress drops over the whole fault plane were estimated to be 18 MPa and 53 MPa, respectively. In addition, the co-seismic displacement field near the fault was analyzed. The results indicate that the features of the co-seismic displacement field were coincident with those of the intensity distribution in the meizoseismal area, implying that the large-scale, large-amplitude and surface-broken thrust dislocation should be responsible for the serious disaster in the near fault area.

Science in China Series D: Earth Sciences, 2009

The moment tensor solution, source time function and spatial-temporal rupture process of the M s6... more The moment tensor solution, source time function and spatial-temporal rupture process of the M s6.4 earthquake, which occurred in Ning’er, Yunnan Province, are obtained by inverting the broadband waveform data of 20 global stations. The inverted result shows that the scalar seismic moment is 5.51×1018 Nm, which corresponds to a moment magnitude of M W 6.4. The correspondent best double couple solution results in two nodal planes of strike 152°/dip 54°/rake 166°, and strike 250°/dip 79°/ rake 37°, respectively. Considering the isoseismals and geological structures in the meizoseismal region, the first nodal plane (strike 152°/ dip 54°/ rake 166°) is preferred to be the seismogenic fault. Thus, the M s6.4 earthquake occurred mainly along a right-lateral fault striking 152°. The source time function shows that the duration time of the earthquake is about 14 s. The most of the energy releases within the first 11 s and in 11–14 s the rupture is weak. The snapshots of the slip-rate indicate that the rupture process has 3 more detailed stages. In the first stage of the first 4 s after rupture initiation, the rupture propagates simultaneously toward both strike and dip directions; in the second stage of the following 3 s, the rupture extends to down-dip direction; and in the third stage, the rupture looks to be scattering on the fault. In general, this earthquake is of bilateral rupture, and the rupture mainly takes place in strike-dip direction. The major ruptured area is in the shape of a diamond with a dimension of 19 km. On the whole fault plane, the maximum slip is about 1.2 m, the average slip is about 0.1 m, the maximum slip-rate is 0.4 m/s and the average slip-rate is 0.1 m/s. The features of the co-seismic theoretical displacement field of the Ning’er earthquake fault, calculated based on the inverted fault parameters, are consistent with those of the observed isoseismals.