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Location:
52 km WSW of Linqiong, China
Period:
20 Apr 2013 00:02:47 - 21 Apr 2013 09:05:23 (1 day 9 hours 2 minutes)
Volcanoes in 100km radius:
None
Earthquakes:
8
M 7.0+:
M 7.9; 58 km W of Tianpeng, China; (12 May 2008) (85km from the swarm center)
No swarms nearby.
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm PS20130420.1 in the Linqiong Region, Sichuan, China

The April 2013 seismic swarm designated PS20130420.1 occurred 52 km west-southwest of Linqiong in Sichuan Province, China. The sequence began at 00:02 on 20 April 2013 and concluded at 09:05 on 21 April 2013, spanning 33 hours and 2 minutes. During this interval, eight earthquakes were recorded, with magnitudes ranging from 4.2 to 6.6 and focal depths between 10 and 15 km.

The mainshock reached magnitude 6.6 at 00:02:47 on 20 April, followed by seven aftershocks. Subsequent events included magnitudes of 5.0, 5.1, 4.2, 5.1, 5.1, 5.0, and a final 5.2 event at 09:05:23 on 21 April. All events clustered at shallow crustal depths typical of the regional tectonic setting.

This swarm took place within the Longmenshan Fault Zone, a northeast-trending thrust system marking the eastern margin of the Tibetan Plateau against the Sichuan Basin. The fault zone accommodates ongoing convergence between the Indian and Eurasian plates, with crustal shortening rates estimated at 3–5 mm per year from geodetic measurements. The 2013 activity lies approximately 85 km from the epicenter of the 12 May 2008 Wenchuan earthquake, a magnitude 7.9 event that ruptured over 240 km along the same fault system.

The 2008 Wenchuan mainshock produced extensive surface rupture and triggered widespread aftershock sequences that persisted for years. Historical records indicate only one prior swarm in the immediate area since 2000, occurring in 2008. The 2013 swarm represents a localized cluster of moderate-magnitude events consistent with post-seismic relaxation and stress redistribution following the 2008 rupture.

Regional geology features Paleozoic to Mesozoic sedimentary rocks overlying Precambrian basement, deformed by Cenozoic thrusting. Seismicity remains elevated due to the fault zone's immaturity and high locking depth, which favors large but infrequent earthquakes interspersed with smaller clusters.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
China Earthquake Networks Center (www.cenc.ac.cn)
Sichuan Provincial Seismological Bureau reports