The M5.0 Suining-Tongnan (China) earthquake of 31 January 2010: A destructive earthquake occurring in sedimentary cover

Abstract

Usually, only crystalline basement is strong enough to store the massive strain energy that can be released in a damaging earthquake. By contrast, sedimentary cover is weak, because of its relatively high porosity and fluids. Therefore, it generally cannot accumulate enough energy for strong earthquakes. On January 31, 2010, a M5.0 earthquake occurred near the border of Suining and Tongnan in China. It excited strong short-period Rayleigh waves Rg, indicative of its shallow focal depth. The focal depth is constrained to less than 4 km, most probably in the range of 1-3 km, by modeling amplitude dependence on the frequency and waveforms of teleseismic depth phases (pP, sP). Because the local Mesozoic sedimentary cover is about 6 km thick, this earthquake should have occurred in the sedimentary cover. Though some shallow earthquakes with magnitudes up to M4 occur in Paleozoic sediments, this earthquake is the first M5 event studied in Mesozoic sedimentary cover. This event provides a rare opportunity to study seismogenic processes of damaging earthquakes in sedimentary basins. Suining-Tongnan Earthquake, sedimentary cover, damaging earthquakeCitation:

Growing seismicity in the Sichuan Basin and its association with industrial activities

“…A temporary station, which was installed~10 hours later by the Chongqing Earthquake Administration, did not record any aftershocks. In agreement with the result of depth phases (Luo et al, 2011), the CMT depth was estimated to be approximately 2.8 km, and thus the earthquake was nucleated in Triassic marine sediment, coincident with the depths of the top boundary of an overpressured gas reservoir (with a pressure ratio as high as~2.2) in the Jialingjiang formation. The strike/dip/rake of the estimated source fault is 223°/48°/122°, showing a rupture areã 2.4 km long along a blind reverse fault consistent with the geological structure and regional stress regime of this area.…”

An Extremely Shallow Mw4.1 Thrust Earthquake in the Eastern Sichuan Basin (China) Likely Triggered by Unloading During Infrastructure Construction

“…For example, the M s 5.7 Wenchuan aftershock in the western Sichuan Basin was located at 3 km depth ; the M s 5.1 Suining-Tongnan earthquake in the center of the Sichuan Basin had a centroid depth of 2 km (Luo et al, 2011); the M L 3.8 Chongqing earthquake in the eastern Sichuan Basin was as shallow as 3 km (Han et al, 2017), and more induced earthquakes with similarly shallow depth (Lei et al, 2019). For example, the M s 5.7 Wenchuan aftershock in the western Sichuan Basin was located at 3 km depth ; the M s 5.1 Suining-Tongnan earthquake in the center of the Sichuan Basin had a centroid depth of 2 km (Luo et al, 2011); the M L 3.8 Chongqing earthquake in the eastern Sichuan Basin was as shallow as 3 km (Han et al, 2017), and more induced earthquakes with similarly shallow depth (Lei et al, 2019).…”

“…induced by large earthquakes or hydraulic fracturing. For example, the M s 5.7 Wenchuan aftershock in the western Sichuan Basin was located at 3 km depth ; the M s 5.1 Suining-Tongnan earthquake in the center of the Sichuan Basin had a centroid depth of 2 km (Luo et al, 2011); the M L 3.8 Chongqing earthquake in the eastern Sichuan Basin was as shallow as 3 km (Han et al, 2017), and more induced earthquakes with similarly shallow depth (Lei et al, 2019). It seems that the Sichuan Basin is probably conditionally slip strengthening or even slip weakening, so that shallow earthquakes in this stable region can be often triggered by transient local stress perturbations or fault strength variety due to external environmental changes.…”

Validating Accuracy of Rayleigh-Wave Dispersion Extracted from Ambient Seismic Noise Via Comparison with Data from a Ground-Truth Earthquake

“…On 30 January 2010, an M s 4.8 earthquake occurred near Suining, a city in the center of Sichuan basin of China (Fig. 1a), and the strong short-period Rg wave and short interval between teleseismic pP and P waves argue for a very shallow depth of 2 km or less (Luo et al, 2011). One coseismic interferogram was formed from a pair of Advanced Land Observation Satellite (ALOS)/PALSAR images (20100119-20100306) using the Jet Propulsion Laboratory/Caltech ROI_PAC software (version 3.1 beta; Rosen et al, 2004).…”