High‐resolution imaging of rapid tremor migrations beneath southern Vancouver Island using cross‐station cross correlations

Peng, Yajun; Rubin, Allan M.; Bostock, M. G.; Armbruster, John G.

doi:10.1002/2015jb011892

Cited by 27 publications

(90 citation statements)

References 39 publications

(106 reference statements)

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“…Peng et al . [] observe rapid tremor migrations near the main front as well. These rapid tremor migrations will be explained as follows in our model.…”

Section: Discussionmentioning

confidence: 96%

Tidal sensitivity of tectonic tremors in Nankai and Cascadia subduction zones

et al. 2015

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Tectonic tremors in subduction zones, which result from slip at the deep plate interface, are known to exhibit a 12.4 h periodicity in their activity, due to tidal influence. Because tidal stress can be calculated quantitatively, the response of the plate interface can yield quantitative information about its frictional property. The relation between tremor rate and tidal stress is investigated, and an exponential relation is widely confirmed, as observed by previous studies. This study particularly focuses on spatial variations of tidal sensitivity, which are compared with spatial variations of tremor duration and amplitude. The sensitivity is quantitatively defined by the exponent of the exponential relation, which can be related to the parameter aσ, or (a − b)σ in the rate‐and‐state friction law, where σ is effective normal stress. On the shallower tremor zone, short‐duration and large‐amplitude tremors occur followed by more sensitive tremors. Meanwhile, deeper tremors with longer duration and smaller amplitude show lower sensitivity, although along‐strike variation also exists. Typical and maximum sensitivities estimated here imply values for aσ or (a − b)σ of about 3 and 1 kPa, respectively. These correlations are consistent with a model in which the plate interface consists of a velocity‐strengthening background with embedded velocity‐weakening regions. The frictional heterogeneity may be statistically characterized by cluster size and density of the velocity‐weakening regions and controls the overall slip behavior. The observed depth dependency of tremor duration, amplitude, and sensitivity implies that frictional heterogeneity is controlled by physical quantities varying with depth, such as temperature or fluid amount.

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“…Peng et al . [] observe rapid tremor migrations near the main front as well. These rapid tremor migrations will be explained as follows in our model.…”

Section: Discussionmentioning

confidence: 96%

Tidal sensitivity of tectonic tremors in Nankai and Cascadia subduction zones

et al. 2015

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“…Observations show that LFEs break multiple times during a large SSE, but often in bursts that have been associated to secondary (smaller-scale) slip transients (e.g. Lengliné et al 2017;Peng et al 2015).…”

Section: Response Of Isolated Asperities To Transient Loadingmentioning

confidence: 99%

“…Tremors are often organized in swarms that migrate. An imbricated hierarchy of tremor migration patterns has been observed in the Cascadia subduction zone (Figure 1) during each recurring episodic tremor and slow-slip event (ETS): large-scale forward tremor propagation along the fault strike direction at about 5-10 km/day, sparsely distributed swarms that propagate about 5 to 50 times faster in the opposite direction ("rapid tremor reversals" or RTRs) (Houston et al 2011), and tremor swarms that propagate even faster along-dip in the vicinity of the main SSE front (Ghosh et al 2010;Peng et al 2015). Bletery et al (2017) found that secondary tremor fronts slow down as they propagate.…”

Section: Introductionmentioning

confidence: 99%

Preprint: Tremor migration patterns and the collective behavior of deep asperities mediated by creep

Luo¹,

Ampuero²

2017

Preprint

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Slow-slip events (SSE) and non-volcanic tremors have revealed a broad spectrum of earthquake behavior, involving entangled seismic and aseismic slip, and offer a unique window into fault mechanics at the bottom of seismogenic zones. A hierarchy of migration patterns of tremors has been observed in the Cascadia subduction zone, including large-scale along-strike tremor propagation and Rapid Tremor Reversals (RTR) migrating in opposite directions with much higher propagation speeds. Here we show that these tremor migration patterns can be reproduced by two end-member models of a fault with heterogeneous mechanical properties, composed of competent asperities embedded in a more frictionally stable, incompetent matrix. In the SSE-driven-tremor model, SSEs are spontaneously generated by the matrix, even in absence of seismic asperities, and drive tremor. In the tremor-driven-SSE model the matrix is stable, it slips steadily in absence of asperities, and SSEs result from the collective behavior of tremor asperities interacting via transient creep in the form of local afterslip fronts. We study these two end-member models through 2D quasi-dynamic multi-cycle simulations of faults governed by rate-and-state friction with heterogeneous frictional properties and effective normal stress, using the earthquake simulation software QDYN . In both models, tremor migration patterns emerge from interactions between asperities mediated by creep transients. The models successfully reproduce forward tremor propagation and RTRs, as well as various other observed tremor migration patterns, without the need to finely tune model parameters. Our modeling results suggest that, in contrast to a common view, SSE could be a result of tremor activity. Also, the hierarchical pattern of tremor migrations provides general constraints on fault zone rheology, and the location of RTRs and other tremor patterns might shed light on the finer scale spatial variability of fault properties. We also find that, despite important interactions between asperities, tremor activity rates are proportional to the underlying aseismic slip rate, supporting an approach to estimate SSE properties with high spatial-temporal resolutions via tremor activity.

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“…Gibbons & Ringdal (2009) found that while extended source time functions lead to complicated cross-correlations, the same complications are often observed across a range of stations. Some researchers even use such complex but consistent source time functions to identify tremor without a template event: by searching for waveforms that are similar at multiple stations (Rubin & Armbruster 2013;Armbruster et al 2014;Peng et al 2015;Savard & Bostock 2015). However, for the waveforms to be similar, the stations used must have similar Green's functions.…”

Section: Introductionmentioning

confidence: 99%

“…Only the relative phases of the source time functions will remain. These relative source time function phases may be complicated, but we expect them to be the same among the observing stations, as seen in cross-station tremor processing (Rubin & Armbruster 2013;Armbruster et al 2014;Peng et al 2015;Savard & Bostock 2015). We can therefore determine if the two sources are co-located by examining whether the cross-correlation phases are coherent across stations.…”

Section: Introductionmentioning

confidence: 99%

A phase coherence approach to identifying co-located earthquakes and tremor

Hawthorne

Ampuero

2017

Geophys. J. Int.

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S U M M A R YWe present and use a phase coherence approach to identify seismic signals that have similar path effects but different source time functions: co-located earthquakes and tremor. The method used is a phase coherence-based implementation of empirical matched field processing, modified to suit tremor analysis. It works by comparing the frequency-domain phases of waveforms generated by two sources recorded at multiple stations. We first cross-correlate the records of the two sources at a single station. If the sources are co-located, this cross-correlation eliminates the phases of the Green's function. It leaves the relative phases of the source time functions, which should be the same across all stations so long as the spatial extent of the sources are small compared with the seismic wavelength. We therefore search for cross-correlation phases that are consistent across stations as an indication of co-located sources. We also introduce a method to obtain relative locations between the two sources, based on back-projection of interstation phase coherence. We apply this technique to analyse two tremor-like signals that are thought to be composed of a number of earthquakes. First, we analyse a 20 s long seismic precursor to a M 3.9 earthquake in central Alaska. The analysis locates the precursor to within 2 km of the mainshock, and it identifies several bursts of energy-potentially foreshocks or groups of foreshocks-within the precursor. Second, we examine several minutes of volcanic tremor prior to an eruption at Redoubt Volcano. We confirm that the tremor source is located close to repeating earthquakes identified earlier in the tremor sequence. The amplitude of the tremor diminishes about 30 s before the eruption, but the phase coherence results suggest that the tremor may persist at some level through this final interval.

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High‐resolution imaging of rapid tremor migrations beneath southern Vancouver Island using cross‐station cross correlations

Cited by 27 publications

References 39 publications

Tidal sensitivity of tectonic tremors in Nankai and Cascadia subduction zones

Tidal sensitivity of tectonic tremors in Nankai and Cascadia subduction zones

Preprint: Tremor migration patterns and the collective behavior of deep asperities mediated by creep

A phase coherence approach to identifying co-located earthquakes and tremor

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