Crustal earthquake triggering by modern great earthquakes on subduction zone thrusts

Abstract

Among the many questions raised by the recent abundance of great (M > 8.0) subduction thrust earthquakes is their potential to trigger damaging earthquakes on crustal faults within the overriding plate and beneath many of the world's densely populated urban centers. We take advantage of the coincident abundance of great earthquakes globally and instrumental observations since 1960 to assess this triggering potential by analyzing centroids and focal mechanisms from the centroid moment tensor catalog for events starting in 1976 and published reports about the M9.5 1960 Chile and M9.2 1964 Alaska earthquake sequences. We find clear increases in the rates of crustal earthquakes in the overriding plate within days following all subduction thrust earthquakes of M > 8.6, within about ±10°of the triggering event centroid latitude and longitude. This result is consistent with dynamic triggering of more distant increases of shallow seismicity rates at distances beyond ±10°, suggesting that dynamic triggering may be important within the near field too. Crustal earthquake rate increases may also follow smaller M > 7.5 subduction thrust events, but because activity typically occurs offshore in the immediately vicinity of the triggering rupture plane, it cannot be unambiguously attributed to sources within the overriding plate. These observations are easily explained in the context of existing earthquake scaling laws.

Crustal earthquake triggering by pre-historic great earthquakes on subduction zone thrusts

“…Estimates of the magnitudes of past CSZ thrust earthquakes are required for comparison with inferences about triggering from the modern record and other studies [ Gomberg and Sherrod , ] but are perhaps even more uncertain than their ages. Thus, as for the ages, we attempt simply to capture the range of possibilities based on published results and clearly stated assumptions.…”

“…Was the 1200–900 cal years B.P. clustering of crustal earthquakes triggered by a M > 8.6 paleo‐earthquake on the Cascadia plate boundary, as the modern record from other subduction zones would suggest [ Gomberg and Sherrod , ]? Could smaller CSZ thrust paleo‐earthquakes have triggered the cluster?…”

“…The most recent great ( M > 8.0) subduction thrust earthquakes, particularly the 2011 M 9.0 Tohoku‐oki Japan earthquake [ Asano et al ., ; Ishibe et al ., ; Kato et al ., ; Nettles et al ., ; Yoshida et al ., ], raised concerns about the potential for triggered crustal earthquakes to threaten major population centers or power‐generating facilities in subduction zones that include Tokyo, Jakarta, Manila, Lima, Santiago (Chile) [ Bilham , ], and in the Cascadia subduction zone (CSZ) of the Pacific Northwest, U.S.. These concerns motivated us to study possible triggering of crustal earthquakes by subduction thrust events using the modern global earthquake record, as described in a companion paper [ Gomberg and Sherrod , ]. We also became more concerned about the possibility that a great subduction thrust earthquake triggered an alleged cluster of M > ~6.5 paleo‐earthquakes on multiple crustal faults in the greater Puget Sound region within the same few centuries or less, about 1200–900 cal years B.P.…”

“…(i.e., sidereal years before A.D. 1950) [ Bucknam et al ., ; Sherrod , ; Sherrod et al ., ; Barnett , ; Blakely et al ., ] (Figure ), thus portending similar paroxysms accompanying future great earthquakes. We independently approached questions of immediate triggering [see Gomberg and Sherrod , ] and longer term triggering (herein), but discuss if and how results of both may relate to one another in section .…”

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

“…More recently, other studies have documented that surface waves generated by large earthquakes can trigger seismicity at large distances (Hill and Prejean, 2007;Velasco et al, 2008;González-Huízar et al, 2012;Van Der Elst and Brodsky, 2013;Gomberg and Sherrod, 2014). The triggered seismicity can occur instantaneously during the passing of the seismic waves (Hill and Prejean, 2007), but a significant increase of seismicity can also occur several days or even weeks after the passing of the waves (e.g., Pankow et al, 2004;Pollitz et al, 2012).…”