The 2011 M w 9.0 Tohoku, Japan, earthquake triggered deep tectonic tremor and shallow microearthquakes in numerous places worldwide. Here, we conduct a systematic survey of triggered tremor in regions where ambient or triggered tremor has been previously identified. Tremor was triggered in the following regions: south-central Alaska, the Aleutian Arc, Shikoku in southwest Japan, the North Island of New Zealand, southern Oregon, the Parkfield-Cholame section of the San Andreas fault in central California, the San Jacinto fault in southern California, Taiwan, and Vancouver Island. We find no evidence of triggered tremor in the Calaveras fault in northern California. One of the most important factors in controlling the triggering potential is the amplitude of the surface waves. Data examined in this study suggest that the threshold amplitude for triggering tremor is ∼0:1 cm=s, which is equivalent to a dynamic stress threshold of ∼10 kilopascals. The incidence angles of the teleseismic surface waves also affect the triggering potentials of Love and Rayleigh waves. The results of this study confirm that both Love and Rayleigh waves contribute to triggering tremor in many regions. In regions where both ambient and triggered tremor are known to occur, tremor triggered by the Tohoku event generally occurred at similar locations with previously identified ambient and/or triggered tremor, further supporting the notion that although the driving forces of triggered and ambient tremor differ, they share similar mechanisms. We find a positive relationship between the amplitudes of the triggering waves and those of the triggered tremor, which is consistent with the prediction of the clock-advance model.

Seismic waves from large earthquakes have been shown to trigger seismicity large distances from a mainshock, and this is termed remotely or dynamically triggered seismicity. We performed a global search for seismicity potentially triggered by the seismic waves from the 2011, M9.0, Tohoku‐Oki, Japan Earthquake. Using seismograms from global seismic networks and an event catalog, we search for earthquakes and tremors instantaneously triggered during the passing of the seismic waves, as well as for statistically significant changes in local and global seismic rates after the passing of the waves. For earthquakes, we find potential cases of instantaneous triggering in the United States, Russia, China, Ecuador and Mexico, while for tremors we find evidence for triggering in Taiwan, Armenia, Cuba and the United States. In addition, we observed a potential case of delayed triggering of larger magnitude earthquakes (including a M5.2) in Baja California, Mexico.

Changes in the static stress can trigger nearby earthquakes that occur within a few fault lengths from the causative event. Transient stresses caused by passage of surface waves commonly trigger events at remote distances, yet little is documented or understood about the processes and stresses necessary for remote triggering. To understand the causative stresses and environments behind remote, or dynamic, triggering, we must decipher the stresses caused by the passage of the surface waves in relation to the local stress field and fault conditions where the triggered events occur. In this study, we model the change in the stress field that the passing of Rayleigh and Love waves causes on a fault plane of arbitrary orientation relative to the direction of propagation of the waves, and we apply a Coulomb failure criterion to calculate the potential of these stress changes to trigger reverse, normal, or strike‐slip failure. We compare these model results with data from dynamically triggered earthquakes in the Australian Bowen Basin, an area with low seismicity and mapped regional stress and that is at the margin of a stable continental craton. Our data analysis shows that for this region, surface waves arriving at 45° from the average strike direction are the most likely to trigger local seismicity. This agrees with our observations.

We provide additional evidence of tectonic tremor in Cuba triggered by the 2010 M w 8.8 Maule, Chile, and the 2011 M w 9.0 Tohoku-Oki, Japan, earthquakes. The high-frequency tremor signals are modulated by long-period surface waves, similar to triggered tremors observed in other tectonically active regions. We are able to locate two tremor sources triggered by the Tohoku-Oki earthquake near the east-west trending Oriente fault around Guantanamo Bay. The tremor around Guantanamo Bay was triggered primarily by a Love wave of the Maule mainshock, and by both Love and Rayleigh waves of the Tohoku-Oki mainshock. This is consistent with frictional failures at a vertical strike-slip fault under a Coulomb failure criterion.

International audienceTriggering studies provide an important tool for understanding the fundamental physics of how faults slip and interact, and they also provide clues about the stress states of faults. In this study, we explore how seismic waves from the 27 February 2010 Mw8.8 Maule, Chile mainshock interact with the left lateral strike-slip Enriquillo–Plantain Garden Fault (EPGF) and surrounding reverse faults in the southern Haiti peninsula. The Chile mainshock occurred 6,000 km away and just 46 days after the 12 January 2010 Mw7.0 Haiti earthquake, a tragic event which activated multiple faults in the southern Haiti peninsula. During the surface waves of the Chile mainshock, several tectonic tremor signals were observed, originating from south of the EPGF trace. Cross-correlation of the triggered tremor and transient stresses resolved onto to the EPGF indicates that the Love wave of the Chile mainshock was the primary driving mechanism of the triggered deep shear slip and tremor signals, as opposed to dilatational stress changes generated by the Rayleigh wave. We also searched for any influence of transient stresses on Haiti aftershock activity by applying the matched filter technique to multiple days of seismic data around the time of the Chile mainshock. While we identified a slight increase in Haiti aftershock activity rate, the rate changes were significant only when small magnitude events were included in the significance tests. These observations are generally consistent with recent inferences that deep tectonic tremor is more sensitive than shallow earthquakes to external stress perturbations