Comparative Analysis on the Characteristics of Low‐Frequency Energy Released by the Wenchuan Earthquake and Kunlun Mountains Earthquake

Abstract

AbstractThe Mw7.9 Wenchuan earthquake of 12 May 2008 and Mw7.8 Kunlun Mountain earthquake of 14 November 2001 have equivalent energy magnitudes. However, the characteristics of the fault rupture processes and the geographical positions of these two great earthquakes are very different, and the damage and the public attention of the Kunlun Mountain earthquake are far less than the Wenchuan earthquake. The seismic wave energy information generated by great earthquakes is very rich. High‐frequency energy of a big quake decays quickly within short time in a small scope, while low‐frequency energy especially very low‐frequency energy decays slowly, and can spread many laps around the Earth before consumed. We employ the spectral element method incorporated with large‐scale parallel computing technology to investigate the characteristics of seismic wave propagation excited by the two great earthquakes. The transverse isotropic PREM (Preliminary Reference Earth Model) model is employed as a prototype for the numerical global Earth model. The Crust2.0 and S20RTS models are taken into consideration. These wave propagation processes are simulated by solving three‐dimensional elastic wave governing equations. The visualization of the numerical results displays the profile with three components of the seismic wave propagation. Our calculation displays the thrusting and strike‐slip of the source rupture processes of the Wenchuan earthquake and the left‐lateral strike‐slip of the source rupture process of the Kunlun Mountain earthquake, respectively. Comparison of low‐frequency energy information of synthetic seismograms excited by the two earthquakes shows that the energy at low‐frequency oscillation modes is broadly equivalent, but the energy of the Kunlun Mountain earthquake is slightly smaller than that of the Wenchuan event. The results also demonstrate that the frequency components are almost the same at low‐frequency displacement amplitude spectra recorded at different stations between the two great earthquakes, but the energy is obviously different. These can further reveal that the characteristics of Earth's oscillation triggered by large earthquakes with different source ruptures are different, and the characteristics of Earth's oscillations recorded by different stations are also different.