Structural geometry of the source region for the 2013 Mw 6.6 Lushan earthquake: Implication for earthquake hazard assessment along the Longmen Shan

Li, Yiquan; Jia, Dong; Wang, Maomao; Shaw, John H.; He, Jun; Lin, Aiming; Xiong, Lin; Rao, Gang

doi:10.1016/j.epsl.2014.01.018

Cited by 87 publications

(83 citation statements)

References 62 publications

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“…The base of the sedimentary section as defined in this study is the contact between these Sinian sedimentary rocks and mid‐Proterozoic metamorphic igneous rocks. The top of the crystalline basement horizon defined in this study was compiled from published isopach maps [ Editorial Group of Petroleum Geology of Sichuan Oil Field (EGPGSOF) , ], data from recent petroleum wells, and interpretation on seismic reflection profiles (e.g., Figure ) [ Jia et al ., ; Hubbard et al ., ; Li et al ., ; Guo et al ., ; Wang et al ., ].…”

Section: Data and Modeling Methodsmentioning

confidence: 99%

Three‐dimensional seismic velocity structure in the Sichuan basin, China

et al. 2016

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We present a new three‐dimensional velocity model of the crust in the eastern margin of the Tibetan Plateau. The model describes the velocity structure of the Sichuan basin and surrounding thrust belts. The model consists of 3‐D surfaces representing major geologic unit contacts and faults and is parameterized with Vp velocity‐depth functions calibrated using sonic logs. The model incorporates data from 1166 oil wells, industry isopach maps, geological maps, and a digital elevation model. The geological surfaces were modeled based on structure contour maps for various units from oil wells and seismic reflection profiles. These surfaces include base Quaternary, Mesozoic, Paleozoic, and Proterozoic horizons. The horizons locally exhibit major offsets that are compatible with the locations and displacements of important faults systems. This layered, upper crustal 3‐D model extends down to 10–15 km depth and illustrates lateral and vertical variations of velocity that reflect the complex evolution of tectonics and sedimentation in the basin. The model also incorporates 3‐D descriptions of Vs and density for sediments that are obtained from empirical relationships with Vp using direct measurements of these properties in borehole logs. To illustrate the impact of our basin model on earthquake hazards assessment, we use it to calculate ground motions and compare these with observations for the 2013 Lushan earthquake. The result demonstrates the effects of basin amplification in the western Sichuan basin. The Sichuan CVM model is intended to facilitate fault systems analysis, strong ground motion prediction, and earthquake hazards assessment for the densely populated Sichuan region.

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Section: Data and Modeling Methodsmentioning

confidence: 99%

Three‐dimensional seismic velocity structure in the Sichuan basin, China

et al. 2016

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“…Seismic and geological interpretations suggest that the seismogenic fault is a gently dipping approximately 30°frontal blind thrust [Wang et al, 2014b;Li et al, 2014]. However, the relocated aftershocks and focal mechanism solution (Figure 1a) indicate that the seismogenic fault dips at~47°to the NW [Zeng et al, 2013].…”

Section: Introductionmentioning

confidence: 99%

Seismotectonics of the 2013 Lushan M_w 6.7 earthquake: Inversion tectonics in the eastern margin of the Tibetan Plateau

et al. 2017

Geophysical Research Letters

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On 20 April 2013, an unexpected Mw 6.7 earthquake occurred in Lushan County at the southern Longmen Shan, the eastern margin of the Tibetan Plateau. A high‐resolution seismic reflection profile was combined with near‐surface geological data, earthquake relocation and geodetic measurements, and a recent deep artificial seismic reflection profile to identify the active fault and seismotectonics of this earthquake. Three‐dimensional imaging of the aftershocks was used to identify two planar faults that together form a y shape (f1 and f2). Seismic interpretations suggest that fault f1 did not break through the overlying Mesozoic and Cenozoic rocks and is a typical blind fault. Geodetic measurements suggest that the coseismic deformation is consistent with the geometry and kinematics of shear fault‐bend folding. Deep seismic data indicate the syndepositional nature of fault f1 a preexisting normal fault older than the Triassic, which underwent positive inversion tectonics during the Late Cenozoic. A thrust fault f3 converges with f1 at a depth of approximately 12 km with an accumulated slip 3.6 km. This 2013 Lushan earthquake triggered by blind faults is a hidden earthquake. Blind and reactivated faults increase the potential risk and uncertainty related to earthquakes in the eastern margin of the Tibetan Plateau.

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“…For example, Chen et al [12] calculated the moment deficit along the unruptured segments of the LMSF between the 2008 Mw 7.9 Wenchuan and the 2013 Mw 6.6 Lushan rupture zones, and stated there is a high seismic risk on the "seismic gap", which might be capable of generating an Mw 6.6 earthquake. Li et al [20] and Liu et al [14,15] also suggested that the unruptured segment is most likely to produce a large earthquake (M~7) by interpreting results from 3D a numerical interseismic deformation simulation and co-seismic Coulomb stress calculation. On the other hand, both geologic trenches and seismic profiling suggest a low probability of a large earthquake along the gap in the near future [13,46], which is also supported by our fault-coupling model.…”

Section: Seismic Hazard Along the Southern Lmsfmentioning

confidence: 99%

“…We discretize the fault model into many sub-faults, with an average 50 km along the strike and depth-dependent sampling along the downdip, which include 0. 1,4,8,12,16,20, and 30 km at depth. We solve φ for each sub-fault, which is further divided into 8 km × 4 km patches along the strike and downdip and interpolated by the bilinear method ( Figure S3).…”

Section: Modeling Strategiesmentioning

confidence: 99%

“…Thus, a large number of studies have focused on their relationship and have obtained discrepant results (e.g., [12,14,[17][18][19]). For instance, there are debates about whether the 2013 Mw 6.6 Lushan earthquake was an aftershock of the 2008 Mw 7.9 Wenchuan earthquake (e.g., [12,14,17,19,20]). Moreover, previous studies indicated that both the co-seismic rupture and postseismic relaxation due to the 2008 event may have increased the stress level on the southern LMSF, which triggered the 2013 event (e.g., [14,18,21]).…”

Section: Introductionmentioning

confidence: 99%

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GPS-Derived Fault Coupling of the Longmenshan Fault Associated with the 2008 Mw Wenchuan 7.9 Earthquake and Its Tectonic Implications

Zhang

Shan

et al. 2018

Remote Sensing

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Abstract:Investigating relationships between temporally-and spatially-related continental earthquakes is important for a better understanding of the crustal deformation, the mechanism of earthquake nucleation and occurrence, and the triggering effect between earthquakes. Here we utilize Global Positioning System (GPS) velocities before and after the 2008 Mw 7.9 Wenchuan earthquake to invert the fault coupling of the Longmenshan Fault (LMSF) and investigate the impact of the 2008 Mw 7.9 Wenchuan earthquake on the 2013 Mw 6.6 Lushan earthquake. The results indicate that, before the 2008 Mw 7.9 Wenchuan earthquake, fault segments were strongly coupled and locked at a depth of~18 km along the central and northern LMSF. The seismic gap between the two earthquake rupture zones was only locked at a depth < 5 km. The southern LMSF was coupled at a depth of~10 km. However, regions around the hypocenter of the 2013 Mw 6.6 Lushan earthquake were not coupled, with an average coupling coefficient~0.3. After the 2008 Mw 7.9 Wenchuan earthquake, the central and northern LMSF, including part of the seismic gap, were decoupled, with an average coupling coefficient smaller than 0.2. The southern LMSF, however, was coupled to~20 km depth. Regions around the hypocenter of the 2013 Mw 6.6 Lushan earthquake were also coupled. Moreover, by interpreting changes of the GPS velocities before and after the 2008 Mw 7.9 Wenchuan earthquake, we find that the upper crust of the eastern Tibet (i.e., the Bayan Har block), which was driven by the postseismic relaxation of the 2008 Mw 7.9 Wenchuan earthquake, thrust at an accelerating pace to the Sichuan block and result in enhanced compression and shear stress on the LMSF.

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Structural geometry of the source region for the 2013 Mw 6.6 Lushan earthquake: Implication for earthquake hazard assessment along the Longmen Shan

Cited by 87 publications

References 62 publications

Three‐dimensional seismic velocity structure in the Sichuan basin, China

Three‐dimensional seismic velocity structure in the Sichuan basin, China

Seismotectonics of the 2013 Lushan M_w 6.7 earthquake: Inversion tectonics in the eastern margin of the Tibetan Plateau

GPS-Derived Fault Coupling of the Longmenshan Fault Associated with the 2008 Mw Wenchuan 7.9 Earthquake and Its Tectonic Implications

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Structural geometry of the source region for the 2013 Mw 6.6 Lushan earthquake: Implication for earthquake hazard assessment along the Longmen Shan

Cited by 87 publications

References 62 publications

Three‐dimensional seismic velocity structure in the Sichuan basin, China

Three‐dimensional seismic velocity structure in the Sichuan basin, China

Seismotectonics of the 2013 Lushan Mw 6.7 earthquake: Inversion tectonics in the eastern margin of the Tibetan Plateau

GPS-Derived Fault Coupling of the Longmenshan Fault Associated with the 2008 Mw Wenchuan 7.9 Earthquake and Its Tectonic Implications

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Seismotectonics of the 2013 Lushan M_w 6.7 earthquake: Inversion tectonics in the eastern margin of the Tibetan Plateau