Source Model and Simulated Strong Ground Motion of the 2021 Yangbi, China Shallow Earthquake Constrained by InSAR Observations

On 21 May 2021, an Mw 6.1 earthquake, causing considerable seismic damage, occurred in Yangbi County, Yunnan Province of China. To better understand the surface deformation pattern, source characteristics, seismic effect on nearby faults, and strong ground motion, we processed the ascending and descending SAR images using the interferometric synthetic aperture radar (InSAR) technique to capture the radar line-of-sight (LOS) directional and 2.5-dimensional deformation. The source model was inverted from the LOS deformation observations. We further analyzed the Coulomb failure stress (CFS) transfer and peak ground acceleration (PGA) simulation based on the preferred source model. The results suggest that the 2021 Yangbi earthquake was dextral faulting with the maximum slip of 0.9 m on an unknown blind shallow fault, and the total geodetic moment was 1.4 × 1018 Nm (Mw 6.06). Comprehensive analysis of the CFS transfer and geological tectonics suggests that the Dian–Xibei pull-apart basin is still suffering high seismic hazards. The PGA result demonstrates that the seismic intensity of this event reached up to VIII. The entire process from InSAR deformation to source modeling and strong ground motion simulation suggests that the InSAR technique will play an important role in the assessment of earthquake disasters in the case of the shortening of the SAR imaging interval.

Strong ground motion simulation of the 27 May 2006 Yogyakarta earthquake using Empirical Green’s Function

On May 27, 2006, 05:54 am local time, a moderate crustal earthquake of magnitude Mw 6,3 struck the Yogyakarta province, especially in the Bantul regency in the south part of the province. The earthquake damaged or destroyed more than 400,000 houses and buildings and caused more than 5,700 people killed. Several earthquake stations recorded the ground vibration caused by the mainshock very well, except at the stations closest to the earthquake source, namely YOGI in Gamping, West of Yogyakarta, which experienced saturation due to significant vibration. Therefore, information about the maximum ground acceleration near the source is yet not known. We model the ground vibrations near the earthquake source using a stochastic Green’s Function approach to obtain information about the ground motions’ maximum amplitude. The earthquake source parameters we referred to is the moment tensor solution from the Harvard Moment Tensor. The calculations show that the amplitude is consistent with observations recorded at the BJI Banjarnegara (0.04g) and YOGI Yogyakarta (0.3g).

Strong ground motion simulation of the 2013 MS 7.0 Lushan, China, earthquake

<p>The near source strong ground motions of the 2013 MS 7.0 Lushan, China, earthquake were simulated using empirical Green's function (EFG) method. At first, we estimated the amount and location of strong motion generation areas (SMGA) based on the character of both slip distributions from far-field seismic inversion and the envelopes of recorded acceleration from main shock, and determined the amount of subfaults on SMGAs referring to the scaling law introduced by Somerville et al.. Then, we implemented the genetic algorithm searching for the optimized source parameters. Based on the source models, we synthetized the waveforms for the 30 stations selected near the source region. Our results show that the comparison between the synthetic waveforms and the observed records agree very well with each other, especially for the part of high-frequency larger than 1.0 Hz. We found that there are two obvious SMGAs on the fault, which take the position that the asperities from far-field seismic inversion take. The combined strong motion generation areas we obtained were smaller than those values predicted by extension of the scaling law by Somerville et al..</p>