Abstract
On 20 April 2013, a moment magnitude (Mw) 6.6 earthquake occurred in the Lushan region of southwestern China and caused more than 190 fatalities. In this study, we use geodetic data from nearly 30 continuously operating global positioning system (GPS) stations, two periods of leveling data, and interferometric synthetic aperture radar (InSAR) observations to image the coseismic deformation of the Lushan earthquake. By using the Helmert variance component estimation method, a joint inversion is performed to estimate source parameters by using these GPS, leveling, and InSAR data sets. The results indicate that the 2013 Lushan earthquake occurred on a blind thrust fault. The event was dominated by thrust faulting with a minor left-lateral strike–slip component. The dip angle of the seismogenic fault was approximately 45.0°, and the fault strike was 208°, which is similar to the strike of the southern Longmenshan fault. Our finite fault model reveals that the peak slip of 0.71 m occurred at a depth of ~12 km, with substantial slip at depths of 6–20 km. The estimated magnitude was approximately Mw 6.6, consistent with seismological results. Furthermore, the calculated static Coulomb stress changes indicate that the 2013 Lushan earthquake may have been statically triggered by the 2008 Wenchuan earthquake.
Highlights
On 20 April 2013, an earthquake with a moment magnitude (Mw) of 6.6 struck Lushan County, Ya’an city, Sichuan Province, southwestern China, generating considerable economic losses in the local region [1,2]
Zhao et al [5] used waveform data from the Global Seismographic Network (GSN)/Integrated Research Institutions for Seismology (IRIS), China Earthquake Networks Center (CENC) and Sichuan regional seismic network to perform a focal mechanism inversion; their findings indicated that the mainshock was a thrust earthquake that occurred on a fault with a dip of 45◦
Huang et al [20] used global positioning system (GPS), interferometric synthetic aperture radar (InSAR), leveling, and strong motion data to study different fault geometries based on a homogeneous elastic half-space model and a layered half-space model separately, based on the data residuals, and found that a one-segment fault model constrained by GPS and leveling data can provide a better fit in the near field than other fault models
Summary
On 20 April 2013, an earthquake with a moment magnitude (Mw) of 6.6 struck Lushan County, Ya’an city, Sichuan Province, southwestern China, generating considerable economic losses in the local region [1,2]. The focal mechanism solution released by the United States Geological Survey (USGS) revealed a focal depth of approximately 12.3 km and a fault with a dip of 33◦ [3] After this event, both near-field and far-field broadband digital seismic data were used to constrain the seismic source rupture process and focal mechanism in combination with other relevant information [4,5,6,7,8,9]. We adopted a two-step method to retrieve the source parameters associated with this event to determine the geometry of the seismogenic fault and to estimate the slip distribution along the fault plane using these GPS, leveling, and InSAR data. We calculated the Coulomb stress change based on our preferred slip model and discussed the relationship to the Wenchuan earthquake
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