Nature Geoscience: Seismic velocity reduction and accelerated recovery due to earthquakes on the Longmenshan fault

Shunping Pei, Fenglin Niu, Yehuda Ben-Zion, Quan Sun, Yanbin Liu, Xiaotian Xue, Jinrong Su, and Zhigang Shao

Nature Geosci. 12 (2019) 387-392.

DOI: 10.1038/s41561-019-0347-1


Various studies report on temporal changes of seismic velocities in the crust and attempt to relate the observations to changes of stress and material properties around faults. Although there are growing numbers of observations on coseismic velocity reductions, generally there is a lack of detailed observations of the healing phases. Here we report on a pronounced coseismic reduction of velocities around two locked sections (asperities) of the Longmenshan fault with a large slip during the 2008 Mw 7.9 Wenchuan earthquake and subsequent healing of the velocities. The healing phase accelerated significantly at the southern asperity right after the nearby 2013 Mw 6.6 Lushan earthquake. The results were obtained by joint inversions of travel time data at four different periods across the Wenchuan and Lushan earthquakes. The rapid acceleration of healing in response to the Lushan earthquake provides unique evidence for the high sensitivity of seismic velocities to stress changes. We suggest that stress redistribution plays an important role in rebuilding fault strength.

Insight to the enigmatic origin of the Hangai Dome in central Mongolia

Screen shot 2015-08-28 at 4.04.14 PMThe Hangai Dome in central Mongolia is one of the most bizarre high-elevation places in continental interiors on Earth. The Indian plate collides with the Eurasian plate to its southwest and the Pacific plate subducts under the Eurasian plate to its east. However, the Hangai Dome is very far (thousands of kilometers) away from the plate margin of East Asia where the tectonic plates converge. There have been debates on mechanisms that caused the uplift of Hangai Dome, whether it’s driven by the movement of tectonic plates or caused by the hot mantle rock rising from the deeper interior of the Earth. The new study by Chen et al. (2015, GRL) shows a clearly imaged localized deep mantle upwelling that generated magma in the rigid shell of the Earth (movie). The heat released by the magma makes the lithosphere underlying the dome more buoyant that caused the surface uplift of the dome. This unique example of continental uplift shows that the active mantle also plays an important role in shaping the Earth’s landscape and consequently the ecological habitat. For more detailed information on seismic adjoint tomography technique and data used in constructing the 3-D seismic model, please check out a different article by Chen et al. (2015, JGR) published earlier this year.