Seismogeodetic P‐wave Amplitude: No Evidence for Strong Determinism

Abstract

Whether the final properties of large earthquakes can be inferred from initial observations of rupture (deterministic rupture) is valuable for understanding earthquake source processes and is critical for operational earthquake and tsunami early warning. Initial (P‐wave) characteristics of small to moderate earthquakes scale with magnitude, yet observations of large to great earthquakes saturate, resulting in magnitude underestimation. Whether saturation is inherent to earthquake dynamics or rather is due to unreliable observation of long‐period signals with inertial seismic instrumentation is unclear. Seismogeodetic methods are better suited for broadband observation of large events in the near‐field. In this study, we investigate the deterministic potential of seismogeodetically derived P‐wave amplitude using a dataset of 14 medium‐to‐great earthquakes around Japan. Our results indicate that seismogeodetic P‐wave amplitude is not a reliable predictor of magnitude, opposing the notion of strong determinism in the first few seconds of rupture.

Apparent earthquake rupture predictability

“…Notably, other, more direct lines of evidence that do not suffer from the same limitations show no difference in rupture growth rates for at least several seconds after the onset. This includes peak displacement observations from short-distance seismograms (Meier et al 2016), peak displacement records from local distance ranges (Noda & Ellsworth 2016;Trugman et al 2019) and seismogeodetic waveforms (Goldberg et al 2019).…”

Early Warning for Great Earthquakes From Characterization of Crustal Deformation Patterns With Deep Learning

“…Second, methods that directly calculate earthquake magnitude from body waves or surface wave amplitudes focus on particular frequency bands of the source spectrum, which saturate during large (Mw7.5+) events (Geller, 1976). Third, large earthquakes have durations of several minutes and early onset signals (i.e., the first few seconds of waveforms), utilized by EEW systems, might not contain enough information to forecast the final magnitude of large events (Goldberg et al., 2019; Ide, 2019; Meier et al., 2016, 2017; Melgar & Hayes, 2017; Rydelek & Horiuchi, 2006). Magnitude saturation has consequences for downstream applications that rely on rapid magnitude determination, specifically in the 2011 Tohoku‐oki case both forecasts of the expected shaking and the tsunami amplitudes were drastically underpredicted (Colombelli et al., 2013; Hoshiba & Ozaki, 2014).…”

Improving Early Estimates of Large Earthquake's Final Fault Lengths and Magnitudes Leveraging Source Fault Structural Maturity Information

“…Whether or not it is possible to differentiate between small and large earthquakes early in the rupture process has been widely explored as it is fundamental in making rapid estimates of earthquake size and distribution of potentially damaging ground motions (e.g., Abercrombie, 2019;Colombelli et al, 2014;Danré et al, 2019;Denolle, 2019;Goldberg et al, 2019Goldberg et al, , 2018Ide, 2019, Meier et al, 2017Olson & Allen, 2005;Rydelek & Horiuchi, 2006). Earthquake early warning (EEW), for example, interprets the earliest available data from an earthquake in order to issue warnings to affected areas before the arrival of seismic energy to those regions (e.g., Allen et al, 2009;Behr et al, 2015;Böse et al, 2012;Böse et al, 2018;Cochran et al, 2019;Cua et al, 2009;Meier et al, 2015;Wu & Kanamori, 2008;Wu & Zhao, 2006;Zollo et al, 2006).…”