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Event Detection and Hypocenter Uncertainty Analysis of Induced Earthquakes the Rome Trough, West Virginia

Description: 

Recent induced seismicity (IS) studies in the central and eastern United States found that most earthquakes induced by fracking or wastewater disposal were associated with fluid injections in intervals ≤~1 km above Precambrian basement. However, an IS sequence from 2010 to 2013 in Gilmer County, West Virginia, appears to defy this trend. Earthquakes in this sequence were associated with fracking in the Rome Trough in an interval ~4-5 km above basement. Accurately characterizing this sequence is thus important toward determining existing fault structures that may be activated by future subsurface injections in the region. Earthquakes in the Gilmer County sequence were initially located at shallow depths relative to basement (~3.5–4.5 km above) and because epicenter-to-station distances are relatively large (>~14 km), the calculated focal depths have large uncertainties (+/− 5.8 km). To improve hypocenter determinations and their accuracies and to investigate the causal fault(s), we detected additional events and we determined relative relocations. We used machine learning (ML) packages PhaseNet and GaMMA for phase detection and event association. We used waveform templates derived from the original and ML catalogs within EQcorrscan to match other smaller events. We then leveraged HypoInverse and HypoDD to respectively locate and relocate all verified earthquakes. Preliminary analysis of the Gilmer County sequence revealed >80 located events and nearly 30 relocated events. Relocated hypocenters remain shallow and depict a potential ~4 km long, ~4 km wide fault that strikes ~110° N and dips steeply to the SE and is preferential to failure in the local stress field. However, depth errors for these events remain high after relocation (+/− 2.8 km). Further refinement of our preliminary Gilmer IS results, results from the equivalent analyses of the Braxton County, West Virginia, IS sequence, and quantitative assessments of the location uncertainties will be presented.

Session: Earthquakes, Lithospheric Structure, and Dynamics in Stable Continental Region [Poster]

Type: Poster

Date: 4/17/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Jonathan

Student Presenter: No

Invited Presentation: 

Poster Number: 71

Authors