Ricker-wavelet-like Strain Waves in Shanxi Rift, North China: Atmospheric Loading Effect of the Squall Line

Abstract

Deciphering the physical origin of transient crustal deformation is a difficult challenge in the field of continuous borehole observations of crustal movement because the relevant influencing factors of the phenomenon are extremely multifarious. In the Shanxi Rift, squall lines are a frequently occurring mesoscale convective system. Consequently, strain transients are always observed by the borehole dilatometer network within the Shanxi Rift; however, a fundamental understanding of the transient phenomena induced by squall lines remains elusive. To address this challenge, we adopted a second-order Butterworth band-pass filters (0.5–2 h) to retrieve the borehole volumetric deformations excited by a “dry” squall line from September 21, 2017, that occurred in the Shanxi Rift. The elastic loading of Ricker-wavelet-shaped atmospheric waves induced by squall line, which can cause the main signature of transient deformation to adopt a highly similar shape; this pressure-induced deformation process can last approximately 148–164 min and has a maximum magnitude of approximately 19 nstrain. This work of signal processing clearly identifies the crustal transient induced by a squall line and provides new insights into the origin of some short-lasting crustal deformations in the Shanxi Rift and elsewhere.