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Noisy Stations Make Earthquake Magnitudes Larger

Description: 

The magnitude of a moderate earthquake (e.g., 4<M<6.5) at a teleseismic distance is often estimated by way of the body-wave magnitude (mb). mb is estimated at a station by recording the peak-to-peak amplitude, scaling this by the dominant period, and finally applying an attenuation correction. Using a collection of station mb estimates, it is then possible to estimate the event mb by way of averaging. In order to understand how sensitive mb estimates are to local site conditions, we first estimate background noise levels at stations used by the National Earthquake Information Center (NEIC) for all mb estimates between January 1, 2021, and January 1, 2023 (over 57,000 events). Then, we find a direct correlation between station noise levels and the calculated station mb. For example, stations with background noise levels of 10 nm displacements can routinely produce an overestimate in the station magnitude by 0.5 magnitude units. This suggests that events estimated using only stations in high noise environments (e.g., coastal stations) could produce mb values that are greater than when low-noise stations are used. In order to better understand these phenomena, we produce theoretical and data-driven models that can help to predict the potential bias in station mb estimates.

Session: Network Seismology: Recent Developments, Challenges and Lessons Learned - V

Type: Oral

Date: 5/2/2024

Presentation Time: 03:00 PM (local time)

Presenting Author: Adam

Student Presenter: No

Invited Presentation: 

Authors