Nonlinear attenuation from the interaction between different types of seismic waves and interaction of seismic waves with shallow ambient tectonic stress

Abstract

Strong seismic waves bring rock into frictional failure at the uppermost few hundred meters.Numerous small fractures slip with the cumulative effect of anelastic strain and nonlinear attenuation; these fractures should not distinguish between remote sources of stress. Still, frictional failure criteria are not evident especially when seismic waves change the normal traction on fractures. We identify three earthquakes as examples where consideration of interaction among dynamic stresses from different wave types and ambient tectonic stress provides theoretical predictions of nonlinear attenuation that are potentially testable with single station seismograms. For example, because Rayleigh waves produce shallow horizontal dynamic tension and compression, frictional failure should preferentially occur on the tensile half-cycle if no shallow tectonic stress is present and on the compressional half-cycle if the tectonic stress is already near thrust-faulting failure. We observed neither effect on records from the 2011 M w 9.0 Great Tohoku earthquake. However, Rayleigh waves from this event appear to have brought rock beneath MYGH05 station into frictional failure at 10 m depth and thus suppressed high-frequency S waves. The tensile half-cycle of high-frequency P waves reduced normal traction on horizontal planes beneath station IWTH25 during the 2008 M w 6.9 Iwate-Miyagi earthquake, weakening the rock in shear and suppressing high-frequency S waves. The near-field velocity pulse from the 1992 M w 7.3 Landers earthquake brought the uppermost few hundred meters of granite beneath Lucerne station into frictional failure, suppressing high-frequency S waves. These moderately positive examples support the reality of nonlinear wave interaction, warranting study future strong ground motions.

Nonlinear Suppression of High‐Frequency S Waves by the Near‐Field Velocity Pulse With Reference to the 2002 Denali Earthquake

“…Circles indicate normalized accelerations centered on the origin. The high‐frequency component parallel to the semicircular acceleration path does not change the resolved acceleration much and is not suppressed (Sleep & Nakata, ). Weak loops and kinks in the acceleration curve subparallel to the main trend at 0100, 0700, and 0800 hr may be associated with an unsuppressed weak high‐frequency component.…”

“…The high‐frequency horizontal acceleration was weak, while the initial part of the near‐field velocity pulse passed (Sleep & Nakata, ), as it was at PS10 (Figure ). High accelerations occurred later.…”

“…We quantify this inference in section 4. Our main purpose is to examine apparently nonlinear suppression of high-frequency S waves by the near-field velocity pulse, mainly within the underlying crystalline rock in section 5 (Sleep & Nakata, 2015). The shallow-nonlinearity mechanism is well known from sites with better records (Ghofrani et al, 2013, Wu & Peng, 2011Nakata & Snieder, 2011;Assimaki et al, 2008;Sleep & Nakata, 2017;Bonilla et al, 2019).…”

“…As with PS10, this station was close~1.25 km to the main fault rupture. Sleep and Nakata (2015) noted that the near-field velocity pulse may have suppressed S waves. Three-dimensional nonlinear numerical models (Roten, Olsen, Cui, & Day, 2017) of the Landers earthquake show failure with a flower structure with shallow nonlinear attenuation away from the fault, which supports this inference.…”

Nonlinear Attenuation of S Waves by Frictional Failure at Shallow Depths

“…Then, we discuss simplifications that accrue with the approximation of vertically propagating S waves. For tractable quantification, we apply a nonlinear numerical model for vertically ascending S waves modified from the works of Sleep and Erickson (2014) and Sleep and Nakata (2015) to laterally stratified rocks with wave motion in both horizontal directions. We consider the effects of a deep overpressured aquifer and reverberation of strong S waves in shallow soil as societal applications.…”