Tidal modulation and triggering of low‐frequency earthquakes in northern Cascadia

Royer, A. A.; Thomas, Amanda M.; Bostock, M. G.

doi:10.1002/2014jb011430

Cited by 63 publications

(139 citation statements)

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“…The low effective normal stresses are consistent with the triggering and modulation of tremor by small dynamic stresses such as passing surface waves (Rubinstein et al, 2007) and tidal stresses (Royer et al, 2015;Rubinstein et al, 2008), as well as numerical modeling of slow slip (Liu and Rice, 2007;Rubin, 2008;Segall et al, 2010). Based on the spatial correspondence between the LVZ and the slow earthquake source region, it is tempting to conjecture that high pore-fluid pressures inferred from elevated Vp/Vs values are responsible for deep episodic slow earthquake activity.…”

Section: Accepted M Manuscriptmentioning

confidence: 52%

Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review

2016

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More than a decade after the discovery of deep episodic slow slip and tremor, or slow earthquakes, at subduction zones, much research has been carried out to investigate the structural and seismic properties of the environment in which they occur. Slow earthquakes generally occur on the megathrust fault some distance downdip of the great earthquake seismogenic zone in the vicinity of the mantle wedge corner, where three major structural elements are in contact: the subducting oceanic crust, the overriding forearc crust and the continental mantle. In this region, thermo-petrological models predict significant fluid production from the dehydrating oceanic crust and mantle due to prograde metamorphic reactions, and their consumption by hydrating the mantle wedge. These fluids are expected to affect the dynamic stability of the megathrust fault and enable slow slip by increasing pore-fluid pressure and/or reducing friction in fault gouges.Resolving the fine-scale structure of the deep megathrust fault and the in situ distribution of fluids where slow earthquakes occur is challenging, and most advances have been made using A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTteleseismic scattering techniques (e.g., receiver functions). In this paper we review the teleseismic structure of six well-studied subduction zones (three hot, i.e., Cascadia, southwest Japan, central Mexico, and three cool, i.e., Costa Rica, Alaska, and Hikurangi) that exhibit slow earthquake processes and discuss the evidence of structural and geological controls on the slow earthquake behavior. We conclude that changes in the mechanical properties of geological materials downdip of the seismogenic zone play a dominant role in controlling slow earthquake behavior, and that near-lithostatic pore-fluid pressures near the megathrust fault may be a necessary but insufficient condition for their occurrence.

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Section: Accepted M Manuscriptmentioning

confidence: 52%

Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review

2016

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“…RTRs on southern Vancouver Island were previously identified from templates by Royer et al (2015). However, because spatial resolution was limited to the template distribution, the corresponding time-distance plots possess a discretized and possibly aliased appearance.…”

Section: Discussionmentioning

confidence: 99%

“…Four migrations are identified in black outlines in Figure 8 and mapped in space in Figure 9. Events C and D (∼10 km=hr) correspond to the RTRs that were identified from the template detections by Royer et al (2015). Events A (∼10-15 km=hr) and B (∼10-20 km=hr) were not individually identified within the template detections.…”

Section: Spatiotemporal Clustering Of Lfe Epicentersmentioning

confidence: 92%

“…Seismograms used in this study were collected from various (left to right) The dashed lines are the 20-, 30-, and 40-km contours of Audet's plate interface model. For events C and D, templates used by Royer and Bostock (2013) and Royer et al (2015) to identify these RTRs are shown (diamonds). The closed dashed contour lines with a letter label indicate asperities defined in Figure 7.…”

Section: Data and Resourcesmentioning

confidence: 99%

“…(c) Same as (b) but for template detections. The rapid tremor reversals (RTRs) identified byRoyer and Bostock (2013) andRoyer et al (2015) are shown in black outlines. The color version of this figure is available only in the electronic edition.…”

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confidence: 99%

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Detection and Location of Low‐Frequency Earthquakes Using Cross‐Station Correlation

Savard

Bostock

2015

Bulletin of the Seismological Society of America

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Source geometry and simple propagation of S waves generated by lowfrequency earthquakes (LFEs) in northern Cascadia results in strong waveform coherence on horizontal channels for stations at smaller epicentral distances. As recognized by previous workers, this cross-station similarity can be exploited for detection of LFEs in tremor. We develop a cross-station correlation approach based on waveform coherence and travel-time consistency that exploits a full complement of network stations, and we demonstrate its application to separate arrays on Vancouver Island and Washington state. Our approach yields thousands of impulsive LFE detections per slow-slip episode and hundreds of events between episodes. LFE epicentral distributions reveal the presence of well-defined regions of high asperity density with those regions farther downdip that are active during interepisodic tremor and slow-slip periods. The LFE epicenters also display pronounced spatiotemporal clustering that compares favorably with independent tremor and LFE template catalogs and that defines rapid tremor reversals with complex propagation patterns. The LFE source depths can be estimated for some detections in which P waves are identified on the vertical channel through correlation with the horizontal-component S waveforms. LFE hypocenters cluster between two recently developed plate interface models below southern Vancouver Island. Our approach enables the identification of high signal-to-noise-ratio impulsive LFE detections from targeted regions on the plate boundary for generation of LFE templates to be used in studies of structure and seismogenesis in Cascadia.

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High‐resolution images of tremor migrations beneath the Olympic Peninsula from stacked array of arrays seismic data

Peng

Rubin

2016

Geochem Geophys Geosyst

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Episodic tremor and slip (ETS) in subduction zones is generally interpreted as the manifestation of shear slip near the base of earthquake‐generating portion of the plate interface. Here we devise a new method of cross‐correlating stacked Array of Arrays seismic data that provides greatly improved tremor locations, a proxy for the underlying slow slip, beneath the Olympic Peninsula. This increased resolution allows us to image many features of tremor that were not visible previously. We resolve the spatial transition between the rupture zones of the inter‐ETS and major ETS episodes in 2010, suggesting stress redistribution by the former. Most tremor migrations propagated along the slowly advancing main tremor front during both the inter‐ETS and the major ETS episodes, even though the main front of the former deviated strongly from its usual (along‐dip) orientation. We find a distinct contrast between along‐dip rupture extent of large‐scale rapid tremor reversals (RTRs) to the south and that to the north in our study region that anticorrelates with the locations of inter‐ETS events. These RTRs originate from the main front, similar to smaller‐scale RTRs previously observed at high‐resolution, and many start by propagating along the main front. This could be consistent with RTRs being triggered by a cascading failure of brittle asperities. After initiation, the RTRs repeatedly occupy the same source region, and the early repetitions appear not to be tidally driven. Their stress drop may come from continuing fault weakening processes within the tremor zone, or loading by aseismic slip in surrounding regions.

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Tidal modulation and triggering of low‐frequency earthquakes in northern Cascadia

Cited by 63 publications

References 50 publications

Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review

Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review

Detection and Location of Low‐Frequency Earthquakes Using Cross‐Station Correlation

High‐resolution images of tremor migrations beneath the Olympic Peninsula from stacked array of arrays seismic data

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