Seismic Swarm S20020130.1: Analysis of Activity Northwest of Indian Springs, Nevada

Seismic swarm S20020130.1 was recorded in the region 45 km northwest of Indian Springs, Nevada. The sequence began at 05:23 on 29 January 2002 and concluded at 07:33 on 30 January 2002, spanning 26 hours and 9 minutes. A total of 27 earthquakes were detected during this period, with magnitudes ranging from -0.3 to 0.8 and focal depths between 1 km and 7 km.

The events exhibited a clustered pattern without a dominant mainshock, consistent with swarm behavior driven by fluid migration or localized stress adjustments along fault networks. Early activity on 29 January included multiple events near magnitude 0.0 to 0.2 at depths of 2–7 km. Midday recordings showed slightly higher magnitudes, peaking at 0.8, while later events remained predominantly below 0.5. On 30 January, the sequence tapered with isolated low-magnitude occurrences until termination.

This swarm occurred within the Basin and Range Province of southern Nevada, a region defined by active extensional tectonics. Normal faulting predominates due to crustal stretching, producing numerous north-south trending faults. The area lies near the transition to the Walker Lane belt, where shear deformation contributes to elevated seismicity rates. Historical records indicate recurrent low-magnitude swarms in this setting, often at shallow depths reflecting brittle failure in the upper crust.

Since 1 January 2000, five swarms have been documented in the vicinity. Prior episodes occurred in 2000 (three swarms) and 2002 (two swarms, including the present sequence). These events underscore persistent microseismic activity without escalation to larger earthquakes.

The shallow depths and narrow magnitude range observed in S20020130.1 align with typical swarm characteristics in extensional regimes. Such sequences provide data on fault permeability and stress transfer in tectonically active zones of Nevada.

References

• USGS Earthquake Catalog (historical seismicity data for Nevada)
• Nevada Seismological Laboratory regional reports on Basin and Range tectonics