Exploring remote earthquake triggering potential across EarthScopes' Transportable Array through frequency domain array visualization

Abstract

To better understand earthquake source processes involved in dynamically triggering remote aftershocks, we use data from the EarthScope Transportable Array (TA) that provide uniform station sampling, similar recording capabilities, large spatial coverage, and, in many cases, repeat sampling at each site. To avoid spurious detections, which are an inevitable part of automated time domain amplitude threshold detection methods, we develop a frequency domain earthquake detection algorithm that identifies coherent signal patterns through array visualization. This method is tractable for large data sets, ensures robust catalogs, and delivers higher resolution observations than what are available in current catalogs. We explore seismicity rate changes local to the TA stations following 18 global main shocks (M ≥ 7) that generate median peak dynamic stress amplitudes of 0.001-0.028 MPa across the array. From these main shocks, we find no evidence of prolific or widespread remote dynamic triggering in the continental U.S. within the main shock's wave train or following main shock stress transients within 2 days. However, limited evidence for rate increases exist in localized source regions. These results suggest that for these data, prolific, remote earthquake triggering is a rare phenomenon throughout a wide range of observable magnitudes. We further conclude that within the lower range of previously reported triggering thresholds, surface wave amplitude does not correlate well with observed cases of dynamic triggering. We propose that other characteristics of the triggering wavefield, in addition to specific conditions at the site, will drive the occurrence of triggering at these amplitudes.

Delayed dynamic triggering: Local seismicity leading up to three remote M ≥ 6 aftershocks of the 11 April 2012 M8.6 Indian Ocean earthquake

“…The 16 M ≥ 5.5 triggered earthquakes reported by Pollitz et al [2012] all occur more than 14 h after the IOE, suggesting a failure process must exist that is more complex than Coulomb failure for these larger events [Hill, 2015]. Journal of Geophysical Research: Solid Earth 10.1002/2015JB012243 Gomberg and Prejean, 2013;Linville et al, 2014;Tape et al, 2013]. However, the data resolution in our study areas is not applicable to resolving triggered tremor.…”

“…The 16 M ≥ 5.5 triggered earthquakes reported by Pollitz et al [] all occur more than 14 h after the IOE, suggesting a failure process must exist that is more complex than Coulomb failure for these larger events [ Hill , ]. The IOE did immediately trigger remote tremor and low‐magnitude earthquakes ( M < 4) during the surface wave passage [ Aiken et al , , ; Chao and Obara , ; Fuchs et al , ; Gomberg and Prejean , ; Linville et al , ; Tape et al , ]. However, the data resolution in our study areas is not applicable to resolving triggered tremor.…”

Delayed Dynamic Triggered Seismicity in Northern Baja California, México Caused by Large and Remote Earthquakes

“…The most commonly used approach consists of estimating the peak dynamic stress (PDS) directly from recorded velocity seismograms. In general, the PDS is estimated by multiplying the peak ground velocity (PGV, or maximum peak on the seismogram) by μ=β, in which μ is the shear modulus (∼33;000 MPa) and β is the shear-wave velocity (∼3300 m=s), such that a PGV of 0:1 cm=s corresponds to a PDS of ∼10 kPa (e.g., Hill et al, 1993;Pankow et al, 2004;Velasco et al, 2004;Chao et al, 2013;Linville et al, 2014). For the three mega-earthquakes, broadband three-component seismograms recorded by RESNOM were rotated to the great circle paths, and the PGV was measured in the transverse and vertical components in order to estimate the PDS related to the Love and Rayleigh waves, respectively.…”

Automated Detection of Dynamic Earthquake Triggering by the High‐Frequency Power Integral Ratio

“…However, manual detection is time‐consuming and significantly limits investigations of dynamic triggering over a long time span and/or in a large area. Automatic methods to detect microearthquakes can be applied in this step (Linville et al, ; Velasco et al, ; Wang et al, ), for example, the matched filter technique (Gibbons & Ringdal, ; Z. Peng & Zhao, ; Yang et al, ). However, earthquake templates with even distribution in the research area are important for the matched filter technique, which may be hard to obtain in low seismicity areas.…”

“…However, manual detection is time-consuming and significantly limits investigations of dynamic triggering over a long time span and/or in a large area. Automatic methods to detect microearthquakes can be applied in this step (Linville et al, 2014;Velasco et al, 2016;Wang et al, 2015), for example, the matched filter technique (Gibbons & Ringdal, 2006;Z. Peng & Zhao, 2009;Yang et al, 2009).…”