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Site Response Study in the Greater Boston Area With an Investigation of the Magnitude 3.6 Bliss Corner Earthquake of November 2020

Session: How Well Can We Assess Site Effects So Far? [Poster]

Type: Poster

Date: 4/21/2021

Presentation Time: 03:45 PM Pacific

Description: 

The magnitude 3.6 Bliss Corner, Massachusetts earthquake occurred on November 8th, 2020 causing weak to light shaking (II-IV ShakeMap MMI) along the southern and eastern shores of the state, including in the city of Boston. Although the event only caused minor damage to buildings in the vicinity of the epicenter, there were still app. 29,000 USGS Did You Feel It? reports generated in the Eastern US. Most reports were concentrated in New England, with some reports hundreds of kilometers from the epicenter, possibly indicative of the low attenuating properties of the bedrock underneath the Central and Eastern US (CEUS) region. The Boston Basin and surrounding surficial geology is composed of various soil types including thick layers of resonating clay, sand and till. These glacial sediments and clays are relatively low-velocity (200-300 m/s) and overlay competent, high-velocity (>2000 m/s) bedrock, causing an amplification of seismic waves within engineering frequencies of interest in certain locations (Baise et al. 2016). Using strong and weak motion seismic stations in and around Boston, we compute Horizontal-to-Vertical Spectral Ratios (HVSR) to estimate soil fundamental frequency from both ambient waveforms and the Bliss Corner earthquake. We compare these empirical estimates to synthetic estimates produced using local geologic and engineering data. Additionally, we measure and map Peak Ground Accelerations in the Boston area during the earthquake. Events of this magnitude are rare in Massachusetts, and thus provide an excellent opportunity to understand soil resonance and amplification in a densely populated, urban region.

Presenting Author: Jeremy A. Salerno

Student Presenter: Yes

Authors