Parker Butte, Nevada Earthquake Swarm: December 2024 Analysis

The Parker Butte region in Nevada experienced a significant earthquake swarm designated S20241209.3, beginning at 06:08 on 9 December 2024 and concluding at 16:17 on 29 December 2024. Over 490 hours and 8 minutes, the sequence produced 729 earthquakes. This event marks only the second swarm recorded in the area since 2000, following one in 2002.

Analysis of the first 100 events reveals a pattern typical of swarm activity, with a rapid onset of moderate shaking followed by prolonged aftershock-like sequences. The largest event reached magnitude 5.7 at a depth of 9 km on 9 December at 23:08. Subsequent events clustered between magnitudes 1.0 and 4.2, predominantly at depths of 8–13 km. Early activity included multiple events above magnitude 3.0 within the first hour after the mainshock, such as 3.6 at 12 km depth and repeated 3.2s. Magnitudes generally declined over the following days, with events becoming more scattered in time and mostly below 2.0 after the initial 24 hours.

Nevada lies within the Basin and Range Province, where crustal extension along north-south trending normal faults drives frequent seismicity. Parker Butte sits in a tectonically active corridor influenced by both Basin and Range extension and proximity to the Walker Lane shear zone. This setting produces shallow crustal earthquakes, consistent with the observed depths of 4–15 km in the swarm. Historical records indicate that such swarms can occur without a single dominant mainshock, instead featuring distributed energy release across numerous faults.

The 2024 sequence aligns with the region's long-term behavior. Nevada averages several magnitude 5+ events per decade, often in clusters. Depths in this swarm match typical values for the province, where brittle failure occurs in the upper 15–20 km of crust. No surface rupture was associated with the largest events, suggesting slip on buried or immature fault segments.

Seismic monitoring by regional networks captured the full evolution from initial foreshock-like activity through the peak on 9 December and into the extended tail of microseismicity. The swarm's duration of nearly three weeks and high event count underscore the diffuse nature of strain accommodation in this part of the Basin and Range.

References

USGS Earthquake Catalog Nevada Seismological Laboratory historical data Basin and Range tectonic summaries (USGS Professional Papers)