Crustal earthquake bursts in California and Japan: Their patterns and relation to volcanoes

Abstract

We analyze 153 bursts of earthquakes in southern California and Japan. The burst patterns are similar in southern California and Japan; they fill a spectrum between “swarm‐like” sequences without obvious mainshocks and mainshocks with Omori‐law‐abiding aftershocks. In agreement with our previous work, the “swarm‐like” sequences in Japan have more events, are more voluminous, and tend to expand with time, when compared to “mainshock‐aftershock” type sequences. In both regions, we find that the sequences starting with their largest events tend to be much shorter in duration. Bursts within 50 km of volcanoes are similar in character to those elsewhere except they tend to have longer duration. We hypothesize that swarminess is a proxy for fluid pressure redistribution and/or aseismic slip driving the seismicity bursts, and conversely, the mainshock‐aftershock‐style sequences have end‐member behavior that results solely from a cascade of elastic failures. The complexity of the spatial seismicity distribution does not correlate with the style of swarm observed, indicating that fluid conditions and composition are likely more influential than geometry in determining the patterns we observe.

High‐resolution 3‐D P wave attenuation structure of the New Madrid Seismic Zone using local earthquake tomography

“…[] that New Madrid swarms are related to fluid processes in the crust. The NMSZ findings are consistent with a range of studies associating swarm activity with crustal and/or volcanic fluid processes [i.e., Vidale and Shearer , ; Vidale et al ., ; Shelly et al ., ].…”

Earthquake swarms driven by aseismic creep in the Salton Trough, California

“…East Pacific Rise transform faults, which potentially share the same high heat flow characteristics found in the Salton Trough, exhibit heightened levels of seismicity preceding large strike‐slip earthquakes [e.g., McGuire et al , 2005; Bohnenstiehl et al , 2002] that is reminiscent of the microseismicity increases in the hours before the Salton Trough earthquakes. Vidale and Shearer [2006] and Vidale et al [2006] find that aseismic processes may drive earthquake swarms throughout southern California and in Japan. The 0.1–1 km/h migration velocities observed in Salton Trough swarms also appear to be characteristic of slow slip events in subduction zones both in Cascadia [e.g., Dragert et al , 2001; McGuire and Segal , 2003] and Japan [e.g., Obara , 2002; Shelly et al , 2006; Y. Ishihara, personal communication, 2006].…”

“…Common examples include the aftershock sequences triggered by large crustal earthquakes [e.g., Freed and Lin , 2001; Helmstetter et al , 2006], seismic swarms [e.g., Dieterich , 1992; Vidale and Shearer , 2006; Vidale et al , 2006], and long‐term seismic cycles on major plate boundaries [e.g., Dieterich , 1994; Lapusta et al , 2000]. The stressing rate changes associated with seismic swarms are often explained as a response to fault creep, fluid or magmatic events [e.g., Hill et al , 1975; Smith et al , 2004; Hainzl and Ogata , 2005; McGuire et al , 2005; Vidale and Shearer , 2006; Vidale et al , 2006], and have been exploited for evaluating earthquake triggering models in magmatically dominated environments [e.g., Dieterich et al , 2000; Toda et al , 2002]. Davis et al [2001, 2004] use borehole pressure transients to infer that aseismic spreading processes trigger earthquake swarms along the Juan de Fuca ridge, but no geodetic observations exist to verify this hypothesis.…”

Adaptive Smoothing of Seismicity in Time, Space, and Magnitude for Time-Dependent Earthquake Forecasts for California

“…Although the empirical laws appear to capture the firstorder or average characteristics of earthquake clustering well, much evidence has been claimed to show that seismicity frequently deviates from this gross description (e.g., Vidale et al, 2006;Ben-Zion, 2008;Enescu et al, 2009;Shearer, 2012;Hainzl, 2013). To capture potential deviations, we wish to develop more flexible, purely data-driven models.…”

“…To capture potential deviations, we wish to develop more flexible, purely data-driven models. For example, the Omori-Utsu law is widely observed to hold during aftershock sequences (e.g., Utsu et al, 1995), but variations in the parameters (e.g., Kisslinger and Jones, 1991) and non-Omori-like behavior (e.g., Vidale et al, 2006) have been noted. Similarly, whereas the GutenbergRichter law with exponent b ≈ 1 approximates the magnitude distribution in sufficiently large space-time volumes well (e.g., Kagan, 1997), b-values have been claimed to vary at smaller scales (e.g., Wiemer et al, 1998;Wiemer and Wyss, 2002).…”