Characteristics of subsurface density variations before the 4.20 Lushan M S7.0 earthquake in the Longmenshan area: inversion results

Xuan, Songbai; Shen, Chongyang; Li, Hui; Hu, Hao

doi:10.1007/s11589-015-0109-0

Cited by 7 publications

(5 citation statements)

References 40 publications

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“…In the absence of suitable prior constraints, the solution of gravity potential field inversion has low vertical resolution, and is not unique. Since several previous studies have found gravity changes before the M S 7.0 Lushan earthquake [26][27][28] , we fixed the inversion depth at the focal depth. Unlike the classic gravity potential inversion method 65 , the BADI method solve the non-unique problem by carrying out inversion and optimization of model parameters based on the time-varying gravity observation data under some prior constraints (Supplementary method 1).…”

Section: Methodsmentioning

confidence: 99%

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Gravity field changes reveal deep mass transfer before and after the 2013 Lushan earthquake

Wang

Chen

Zhuang

et al. 2023

Commun Earth Environ

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The 2013 MS7.0 Lushan earthquake, Sichuan, China, occurred on a blind thrust fault in the southern Longmenshan fault belt. The terrestrial hybrid repeated gravity observation enables us to investigate the redistribution of both surface and deep mass. Here, we find a transient increase in the gravity field about 2 years before the earthquake and a drop after the mainshock. A Bayesian inversion method with spatiotemporal smoothness is employed to extract the apparent density changes. The increase of apparent density on the south of the focal zone is assumed to be related to crustal mass transfer. We introduce a disc-shaped equivalent source model with a homogeneous density to address this hypothesis, and estimate the model parameters by Markov Chain Monte Carlo simulations. As a fluid diffusion footprint is indicated by the seismicity migration in this region, with a fitted diffusion rate of 10 m2 s−1, we conclude that such deep crustal mass transfer may be caused by fluid diffusion.

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Section: Methodsmentioning

confidence: 99%

“…The epicenter of the M S 7.0 Lushan earthquake was in the northern section of the Sichuan THRGO network. Several previous studies have reported gravity changes before the M S 7.0 Lushan earthquake based on the THRGO dataset [26][27][28] . However, how the gravity change relates to the mechanism of the Lushan earthquake occurrence remains debated.…”

mentioning

confidence: 99%

Gravity field changes reveal deep mass transfer before and after the 2013 Lushan earthquake

Wang

Chen

Zhuang

et al. 2023

Commun Earth Environ

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“…Based on the de nition of equivalent water height in satellite gravity measurement, the BADI method employs an apparent density model to μGal μGal construct a relationship between the deep eld source body and the surface observed gravity changes. Unlike the classic gravity potential inversion method (Last and Kubik, 1983;Xuan et al, 2015), the BADI method solve the non-unique problem by carrying out inversion and optimization of model parameters based on the time-varying gravity observation data under some prior constraints (Text S1).…”

Section: Apparent Density Modelingmentioning

confidence: 99%

“…The epicenter is located in the northern section of the Sichuan THRGO network. Several previous studies have reported that there are signi cant gravity changes before the M S 7.0 Lushan earthquake based on the THRGO dataset (Zhu et al, 2013;Hao et al, 2015;Xuan et al, 2015). However, how the gravity change relates to the mechanism of the occurrence of Lushan earthquake remains debated.…”

Section: Introductionmentioning

confidence: 99%

Inversion of time-varying gravity field before and after the 2013 Lushan MS7.0 earthquake

Wang¹,

Chen

Zhuang³

et al. 2022

Preprint

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The 2013 MS7.0 Lushan earthquake, Sichuan, China, occurs on a blind thrust fault in the southern Longmenshan fault belt. The terrestrial hybrid gravity observations enable us to investigate how the deep mass changes before and after the earthquake. Based on the gravity measurement data, we find a transient increase in the gravity field about 2 years before the earthquake and a drop after the mainshock. To find out the cause, a Bayesian inversion method with spatiotemporal smoothness prior is employed to extract apparent density changes. We hypothesize that the significant increase of apparent density over the region on the south of the focal zone might be related to mass transfer in the deep crust. Therefore, we introduce a disc-shaped equivalent source model with a homogeneous density to address this hypothesis. Based on Markov Chain Monte Carlo simulations, we also estimate that the disc-shaped model has a radius of about 96 km, with a thickness of about 1.2 km and a depth of about 14 km. As a fluid diffusion footprint is indicated by seismicity migration in this region, with a fitted diffusion rate of 10 m2/s, we conclude that such deep crustal mass transfer may be caused by fluid diffusion.

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“…As a tentative research, Xuan et al . 20 suggested that the crustal DCs derived from the temporal-spatial gravity-change data may imply the dynamic information related to the pre-earthquake.…”

Section: Introductionmentioning

confidence: 99%

Insight into the preparation of the 2016 MS6.4 Menyuan earthquake from terrestrial gravimetry-derived crustal density changes

Xuan

Jin

Chen³

et al. 2019

Sci Rep

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Geophysical processes of the pre-earthquake activities are difficult to be determined since less pre-seismic signal is observed directly. Crustal density changes derived from the periodical terrestrial gravimetry may provide meaningful deep information for the pre-earthquake cue. In this study, the crustal density changes following the 2016 MS6.4 Menyuan earthquake are estimated using ground-based gravity-change data from 2011 to 2015 in the northeastern Tibetan Plateau. The results show that negative density changes dominate the region between the South Longshou Mountain fault and the Daban Mountain fault except the southeast of this region (the seismic region) during 2011–2012. Positive density changes appeared in the middle crust near the epicenter during 2012–2013 and in the upper and middle crust east of the epicenter approximately 1.5 years before the earthquake (2013–2014), and then negative density changes appeared under and northeast of the epicenter approximately four months before the earthquake (2014–2015). The state of the crustal materials near the seismic region changed from convergence to expansion, in turn, indicating that the characteristics of the deep seismogenic process was corresponding to Amos Nur’s 1974 dilatancy-fluid diffusion model.

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Characteristics of subsurface density variations before the 4.20 Lushan M S7.0 earthquake in the Longmenshan area: inversion results

Cited by 7 publications

References 40 publications

Gravity field changes reveal deep mass transfer before and after the 2013 Lushan earthquake

Gravity field changes reveal deep mass transfer before and after the 2013 Lushan earthquake

Inversion of time-varying gravity field before and after the 2013 Lushan MS7.0 earthquake

Insight into the preparation of the 2016 MS6.4 Menyuan earthquake from terrestrial gravimetry-derived crustal density changes

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