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Earthquake Infrasound Recorded in the Maryland Piedmont

Description: 

The USGS reported an otherwise unremarkable 2.5 MLg earthquake October 27, 2025 21:17 UTC, in the mid-Atlantic Piedmont (4 km above the fall-line) near the Baltimore-Washington DC suburb of Columbia MD. “Did You Feel It?” registered 1227 responses with peak intensities of IV. The USGS network is sparse in this suburban area with the closest station 95 km distant. However, the 2.5 MLg event was recorded on 21 Raspberry Shake (RS) recorders within 51 km and a Raspberry Boom (RB) near the epicenter. Relocation moved 2.8 km westward within 2 km of the dual seismic-infrasound (RS,RB) station, R6CAF. The 0.3 second S-P at the site and 8 second Acoustic-P time locates significantly shallower than the USGS 8 km depth. Additionally, 0.5-3 Hz Rg waveforms, on 31 RS recorders out to 137 km, are inconsistent with a 8 km depth. Correlation processing (10 days before and 30 days after) detected two small aftershocks (ML <1) with no detectable infrasound. The Rg dispersion is consistent with measured dispersion from two 2021 shallow events 21 km NW consistent within the high velocity Piedmont metamorphics. The seismic-to-acoustic conversion event is very well recorded on the RS-RB station. The P and S wave arrivals on the microbarometer are linearly related to the vertical velocity at ~800Pa/(m/s). The first arrival of the pure infrasound signal (I1) at P+5 seconds is consistent with generation at the immediate epicenter, but large acoustic arrivals (I2) at P+8 and P+10 sec suggest more complicated conversions in the epicentral area. And, not correlated with shaking the instrument or the building structure. The record affords a rare opportunity to explore seismic generated infrasound at near epicentral distance. In historic context, in 1993 a series of magnitude 1 - 2.7 earthquakes were felt in close proximity to the 2025 event. Additional felt events occurred in 1996, 2001 and 2002.

Session: New Frontiers in Seismic Observations and Modeling with Innovative Methods and Emerging Data on Earth and Other Planets [Poster]

Type: Poster

Date: 4/17/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Keith L. McLaughlin

Student Presenter: No

Invited Presentation: 

Poster Number: 116

Authors