Seismic Analysis of the November 2005 Earthquake Swarm Near Keeler, California

An earthquake swarm designated S20051106.1 was recorded 56 km northeast of Keeler, California, in Owens Valley. The sequence began at 05:20 on 6 November 2005 and concluded at 07:24 on 8 November 2005, encompassing 56 events over 50 hours and 3 minutes. All events were of low magnitude, with the largest reaching 2.7, consistent with typical swarm behavior in which energy release occurs through numerous small shocks rather than a dominant mainshock-aftershock pattern.

The events clustered at shallow depths, predominantly between 0 and 6 km, with occasional recordings at 7–10 km. A few entries listed negative depths, likely reflecting location uncertainties near the surface. Magnitudes remained below 2.0 for the majority of the swarm, with only four events exceeding 2.0. Temporal distribution showed peak activity during the first 12 hours on 6 November, followed by a gradual decline through 8 November.

Owens Valley lies within the Eastern California Shear Zone, a region of distributed right-lateral shear and east-west extension between the Sierra Nevada and the Basin and Range province. The area is bounded by the Owens Valley Fault to the west and the White Mountains Fault to the east. These structures accommodate a portion of Pacific–North America relative plate motion. Historical seismicity includes the 26 March 1872 Owens Valley earthquake of estimated magnitude 7.4–7.6, which produced surface rupture exceeding 100 km and substantial vertical and horizontal offsets. Ongoing microseismicity reflects continued tectonic strain accumulation and release along these and subsidiary faults.

The 2005 swarm occurred in a setting of Quaternary alluvium and lacustrine deposits overlying metamorphic and granitic basement rocks. Shallow focal depths suggest activity within the upper crust, possibly influenced by fluid migration or minor geothermal effects common in the broader region. No surface rupture or significant damage was associated with the swarm, as expected given the low magnitudes.

Swarm characteristics align with tectonic sequences observed elsewhere in the Walker Lane belt, where clusters of small events can occur without clear triggering by a single large shock. The provided event list illustrates a rapid initial rate of occurrence that decayed over two days, a pattern often linked to pore-pressure changes or aseismic slip at depth.

Further monitoring by regional networks continues to refine the seismic hazard assessment for Inyo County, emphasizing the persistent activity along the Owens Valley and adjacent fault systems.

References

USGS Earthquake Hazards Program – Owens Valley regional tectonics
California Geological Survey – Fault activity map of California
SeismoSight internal swarm classification S20051106.1