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How Can Shaking Observations From the MyShake Smartphone Platform Inform Free-Field Ground Motion Residual Estimates?

Description: 

Ground motion spatial variability can be significant, especially in short-period intensity measure metrics such as pseudo-spectral acceleration (PSA) at periods <1s and peak ground acceleration (PGA). As such, densifying data coverage could potentially reveal finer-level detail when modeling spatial distributions of ground shaking in individual events, as well as in ensemble empirical site response modeling. Acceleration waveforms recorded via the MyShake smartphone app provide one such dataset. MyShake has been delivering ShakeAlert earthquake early warning messages to the public since October 2019. It also provides recorded waveforms using the onboard accelerometer once triggered. This capability has enabled us to construct a waveform database that heavily samples the near-field (epicentral distances <30 km) for M3-5 events. Using MyShake data in California from 2019 to early 2023, we derive predictive models for smartphone-recorded peak accelerations, including one incorporating simple building corrections. Using our models, we calculate MyShake within-event residuals, and compare these to free-field residuals for PGA and 0.3 s PSA. We illustrate how these residuals illuminate small-scale structure in ground motion spatial trends in these, while also matching with independent empirical constraints of free-field site response. Finally, we discuss how MyShake residual correlation with free-field residuals could be used to reduce modeling uncertainties in schemes that model spatial distribution of ground shaking, such as ShakeMap.

Session: From Earthquake Recordings to Empirical Ground-Motion Modelling [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Savvas

Student Presenter: Yes

Invited Presentation: 

Authors