Seismic Swarm S20100508.1: Analysis of Activity near Alberto Oviedo Mota, Baja California

Seismic swarm S20100508.1 was recorded between 03:36 on 7 May 2010 and 22:51 on 13 May 2010, approximately 9 km west-southwest of Alberto Oviedo Mota in Baja California, Mexico. Over 163 hours and 14 minutes, the sequence comprised 95 earthquakes. This event represents one of three swarms documented in the region during 2010 and forms part of a broader pattern of five swarms recorded since 2000, with prior occurrences noted in 2000 and 2001.

The swarm exhibited typical characteristics of clustered seismicity without a dominant mainshock. Magnitudes ranged from 1.4 to 3.9, with the largest events measuring 3.9 on 8 May at 18:53 and again on 12 May at 19:00. Depths were predominantly shallow, spanning 0 to 18 km, and most events clustered between 5 and 14 km. Early activity on 7 May included multiple events above magnitude 3.0, such as the 3.7 quake at 12:02 and paired 3.3 events near midday. Subsequent days featured sustained lower-magnitude releases, with notable spikes including a 3.5 event on 11 May and a 3.4 event on 12 May. Depths showed minor variation, with several events at or near the surface (0 km) on 8 and 11 May, while deeper occurrences reached 18 km on multiple dates.

This distribution indicates a diffuse release of strain across a network of small faults rather than a single rupture plane. The temporal pattern—intense initial bursts followed by intermittent activity—aligns with fluid migration or aseismic slip processes common in the area. No damage or felt reports beyond instrumental detection were associated with these low-to-moderate magnitudes.

Geological Setting and Regional Context

The swarm occurred within the tectonically active Imperial-Mexicali Valley, part of the Pacific–North American plate boundary. Baja California lies on the Pacific Plate, where right-lateral transform motion along the San Andreas system transitions into the Gulf of California rift. Local faulting is dominated by the Cerro Prieto fault zone, a major northwest-trending strike-slip structure with associated geothermal fields. High heat flow and shallow brittle-ductile transitions facilitate swarm-type seismicity through hydrothermal fluid involvement.

Historical seismicity in the region demonstrates recurrent swarm episodes linked to these faults. The 2010 activity fits established patterns of episodic, low-magnitude clustering that relieve accumulated strain without producing large single events. Updated monitoring by regional networks confirms ongoing microseismicity in the same locale, underscoring the persistent tectonic regime.

Implications for Seismic Hazard

Swarm S20100508.1 highlights the value of dense seismic networks in distinguishing swarm behavior from foreshock sequences. While individual events posed minimal hazard, the cumulative energy release and spatial extent provide data for refining fault models in the Cerro Prieto system. Continued observation remains essential given the proximity to populated areas and critical infrastructure in northern Baja California.

References

USGS Earthquake Catalog
Servicio Sismológico Nacional (Mexico)
SeismoSight internal swarm classification database