Seismic Swarm S20020303.1 Near Alberto Oviedo Mota, Baja California
Seismic swarm S20020303.1 occurred in a tectonically active zone of northern Baja California, Mexico, approximately 15 km west of Alberto Oviedo Mota. The sequence began at 23:38 on 2 March 2002 and concluded at 12:25 on 7 March 2002, spanning 108 hours and 47 minutes. During this period, 88 earthquakes were recorded, with magnitudes between 1.6 and 3.4 and focal depths consistently between 5 and 7 km.
The events clustered tightly in both time and space, characteristic of swarm behavior rather than a mainshock-aftershock sequence. Magnitudes remained modest throughout, with the peak event reaching 3.4 on 4 March at 13:12. Most events fell in the 1.7–2.9 range, and activity showed episodic bursts, particularly on 3–4 March and again on 6 March. Depths stayed shallow, consistent with the brittle upper crust in this extensional setting.
The swarm location lies within the Mexicali Valley, part of the Pacific–North American plate boundary. Here, right-lateral transform motion along the Cerro Prieto and Imperial faults accommodates oblique divergence associated with the Gulf of California rift system. The area experiences elevated heat flow linked to nearby geothermal fields, which can facilitate swarm activity through fluid migration and pore-pressure changes. Historical records since 2000 indicate three prior swarms in the immediate region, with one event in 2000 and two in 2002, underscoring recurrent episodic seismicity.
Three kilometers from the swarm centroid, the 4 April 2010 Mw 7.2 Sierra El Mayor–Cucapah earthquake ruptured a complex network of faults, producing surface offsets and widespread aftershocks. This major event highlights the capacity of the same fault system to generate significantly larger ruptures despite the prevalence of smaller swarm-type sequences.
Overall, swarm S20020303.1 exemplifies the low-to-moderate, high-frequency seismicity that defines the northern Baja California margin. Continued monitoring of such clusters aids in understanding strain accumulation and the role of fluids in modulating fault slip within this rapidly deforming continental rift.
References
USGS Earthquake Catalog
Servicio Sismológico Nacional (Mexico)
SeismoSight internal swarm classification records