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

Abstract

The 11 April 2012 M8.6 strike‐slip Indian Ocean earthquake (IOE) was followed by an increase in global seismic activity, with three remote M ≥ 6.0 earthquakes within 24 h. We investigate delayed dynamic triggering by systematically examining three offshore regions hosting these events for changes in microseismic activity preceding the IOE, and during the hours between the IOE surface‐wave arrival and the triggered‐event candidate. The Blanco Fault Zone, USA, and the Tiburón Fault Zone, Mexico, each host a strike‐slip event, and the Michoacán Subduction Zone, Mexico, hosts a reverse event. At these locations we estimate transient Coulomb stresses of ±1–10 kPa during the IOE. Each study area contains a regional seismic network allowing us to examine continuous waveforms at one or more nearby stations. We implement a short‐/long‐term‐average algorithm and template matching to detect events and assess the seismicity with the β‐statistic. Our results indicate low‐magnitude seismicity in the days prior to the IOE and the occurrence of earthquakes during the surface‐wave passage after more than 2 h of transient loading. We find both transtensional tectonic environments respond to the transient stresses with a substantial increase observed in the seismicity rates during the hours after the passage of surface waves. In contrast, seismicity rates remain constant in the subduction zone we investigate during the 14 h delay between the IOE and the large‐magnitude earthquake. The seismicity rate increases we observe occur after many hours of dynamic stresses and suggest the long duration of transient loading initiated failure processes leading up to these M ≥ 6.0 events.

Testing the Influence of Static and Dynamic Stress Perturbations On the Occurrence of a Shallow, Slow Slip Event in Eastern Taiwan

“…In particular, long-lasting (hundred of seconds) dynamic perturbations at moderate to high strain (>100 n or ∼3 kPa) may be an efficient combination for triggering (C. W. Johnson & Bürgmann, 2016;Pollitz et al, 2012). Large dynamic strain perturbations (greater than or equal to ∼500-10 3 n ) during the Nantou shock were sustained about 10-15 s, while destructive earthquakes such as the 2008 Wenchuan, the 2011 Tohoku, and the 2012 Indian Ocean (Sumatra), which triggered tremors and seismicity worldwide (e.g., Gonzalez-Huizar et al, 2012;Peng et al, 2013;Pollitz et al, 2012), show elevated strain in the Ruisui region lasting more than 200 s ( Figure S8).…”

Sediment gravity flows triggered by remotely generated earthquake waves

“…In addition to the studies noted in section 1 that document delayed triggering by seismic waves in many environments, we add examples describing triggering by the Indian Ocean earthquake waves of ≥ M w 5.5 earthquakes globally [ Pollitz et al ., ], of increased rates of tremor [ Chao and Obara , ] and small earthquakes, strains, and seismic velocity changes in Japan [ Delorey et al ., ]. Almost all these triggered phenomena occurred with some delay, including a M w 5.9 earthquake on the Blanco Fracture Zone (BFZ) within the Cascadia Initiative footprint that occurred 14.1 h after the waves had passed [ Johnson and Bürgmann , ].…”

“…Experimentally derived failure threshold estimates range from ~0.1 to 10 J/m 3 with 30 J/m 3 appearing necessary for immediate liquefaction [ Wang , ]. We also used peak strains as a metric, derived from measured peak seismic velocities, as this is often used to assess the potential for triggering liquefaction and landslides [ Wang , ; Wang and Chia , ; ten Brink et al ., ; Jibson and Harp , ], or earthquakes [ Pollitz et al ., ; Johnson and Bürgmann , ]. Typical peak Coulomb stress thresholds associated with seismic wave triggering of earthquakes may be as small as 1 to 10 kPa, or equivalently 0.1 to 1.0 microstrain [ Johnson and Bürgmann , ].…”

Tectonic tremor on Vancouver Island, Cascadia, modulated by the body and surface waves of the Mw 8.6 and 8.2, 2012 East Indian Ocean earthquakes

“…These earthquakes were preferably located in the four lobes of Love‐wave radiation, and most of them occurred where the dynamic shear strain exceeded 10 −7 for 100 s during dynamic wave propagation [ Pollitz et al ., ]. However, none of the 16 M w ≥ 5.5 trigger candidates during the first 6 days occurred before 14 h after the main shock, suggesting delayed triggering by aseismic deformation, fluid flow, or other transient processes [ Johnson and Bürgmann , ; Delorey et al ., ]. Reports of triggered tremor activity from the M w 8.6 event include the Kyushu, Nankai, Kanto, and Hokkaido regions in Japan [ Chao and Obara , ] and near Queen Charlotte Island, Canada [ Aiken et al ., ].…”