The Mariana Islands region lies along the Mariana subduction zone, where the Pacific Plate descends beneath the Philippine Sea Plate at rates exceeding 6 cm per year. This tectonic boundary produces the Mariana Trench, the deepest oceanic trench on Earth, reaching approximately 10,984 meters. The resulting volcanic arc and back-arc spreading center create a highly active seismic environment characterized by frequent earthquakes, some exceeding magnitude 7, and associated volcanism.
Seismic swarm PS20100814.1 began at 21:19 on 13 August 2010 and concluded at 12:55 on 15 August 2010, spanning 39 hours and 35 minutes. During this interval, 21 earthquakes were recorded, with the largest event reaching magnitude 6.9 at a depth of 16 km. Subsequent events clustered predominantly at depths of 10–13 km, including a magnitude 6.6 shock and multiple magnitude 5.0–5.7 aftershocks. The swarm’s temporal pattern shows an initial strong shock followed by a rapid sequence of moderate events within the first 24 hours, tapering toward the end of the period.
This activity occurred within a subduction-related setting where intermediate-depth seismicity often reflects slab dehydration and stress transfer along the plate interface. Historical records indicate one prior swarm in the same classification framework since 2000, occurring in 2005, underscoring the episodic nature of clustered seismicity in the region.
The 2010 swarm contributed to ongoing monitoring of strain accumulation along the Mariana arc, where great earthquakes remain possible given the locked segments of the subduction interface. Regional geology features andesitic stratovolcanoes such as Anatahan and Pagan, whose eruptive histories correlate with tectonic stress changes detected through seismic networks.
References
SeismoSight internal swarm classification PS20100814.1
USGS Earthquake Catalog (Mariana Islands region tectonics)
NOAA Pacific Tsunami Warning Center regional summaries