High‐resolution images of tremor migrations beneath the <scp>O</scp>lympic <scp>P</scp>eninsula from stacked array of arrays seismic data

Peng, Yajun; Rubin, Allan M.

doi:10.1002/2015gc006141

Cited by 24 publications

(49 citation statements)

References 46 publications

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“…After sorting the remaining duplicate detections into their proper families, our final catalog includes to 32,387 unique LFEs sorted into 43 families (Figure ). The locations of LFE families in our catalog are similar to LFEs in other catalogs beneath the Olympic Peninsula from Royer and Bostock [] and Peng and Rubin []. Royer and Bostock [] created a catalog using a method similar to this work but did not use data from the AofA.…”

Section: Resultsmentioning

confidence: 61%

Evidence for a scale‐limited low‐frequency earthquake source process

2017

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We calculate the seismic moments for 34,264 low‐frequency earthquakes (LFEs) beneath the Olympic Peninsula, Washington. LFE moments range from 1.4 × 1010 to 1.9 × 1012 N m (Mw = 0.7–2.1). While regular earthquakes follow a power law moment‐frequency distribution with a b value near 1 (the number of events increases by a factor of 10 for each unit increase in Mw), we find that while for large LFEs the b value is ~6, for small LFEs it is <1. The magnitude‐frequency distribution for all LFEs is best fit by an exponential distribution with a mean seismic moment (characteristic moment) of 2.0 × 1011 N m. The moment‐frequency distributions for each of the 43 LFE families, or spots on the plate interface where LFEs repeat, can also be fit by exponential distributions. An exponential moment‐frequency distribution implies a scale‐limited source process. We consider two end‐member models where LFE moment is limited by (1) the amount of slip or (2) slip area. We favor the area‐limited model. Based on the observed exponential distribution of LFE moment and geodetically observed total slip, we estimate that the total area that slips within an LFE family has a diameter of 300 m. Assuming an area‐limited model, we estimate the slips, subpatch diameters, stress drops, and slip rates for LFEs during episodic tremor and slip events. We allow for LFEs to rupture smaller subpatches within the LFE family patch. Models with 1–10 subpatches produce slips of 0.1–1 mm, subpatch diameters of 80–275 m, and stress drops of 30–1000 kPa. While one subpatch is often assumed, we believe 3–10 subpatches are more likely.

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Section: Resultsmentioning

confidence: 61%

Evidence for a scale‐limited low‐frequency earthquake source process

2017

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“…However, the absolute RTR stress drop has at least a factor of 2 uncertainty, as the relevant shear modulus may be a factor of 1.5 lower than our assumed value (see section 5.5), and incorrect assumptions about the Green's functions may have caused us to overestimate the stress drop by a factor of 1.3 (see section 5.5). The tidal load is an appealing source of stress given the observed tidal triggering of RTRs [ Thomas et al ., ; Royer et al ., ; Peng and Rubin , ] and tremor well behind the front [ Houston , ; Royer et al ., ]. We note, however, that the tidal load is cyclic.…”

Section: Discussionmentioning

confidence: 99%

“…For comparison, most tremor in the main slow slip front occurs over 1 to 2 days, within a roughly 10 km region [ Wech and Creager , ; Ghosh et al ., ; Royer et al ., ; Bostock et al ., ; Peng and Rubin , ]. 2.5 cm of slip during a one to 2 day period suggests average slip rates of 0.1 to 0.2 μm/s, a factor of a few to 10 smaller than slip rates estimated for RTRs.…”

Section: Implied Moments Slips and Stress Dropsmentioning

confidence: 96%

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Variations in slow slip moment rate associated with rapid tremor reversals in Cascadia

Hawthorne

Bostock

Royer

et al. 2016

Geochem Geophys Geosyst

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During large slow slip events, tremor sometimes propagates in the reverse along‐strike direction for a few hours, at speeds 10 to 40 times faster than the forward propagation. We examine the aseismic slip that underlies this rapidly propagating tremor. We use PBO (Plate Boundary Observatory) borehole strainmeter data to search for variations in the slow slip moment rate during 35 rapid tremor reversals (RTRs) that occurred beneath Vancouver Island. The strain records reveal that, on average, the strain rate increases by about 100% ( ±30%) during RTRs. Given the Green's functions expected for slip in the RTR locations, these strain rate increases imply 50 to 130% increases in the aseismic moment rate. The median moment released per RTR is between 8 and 21% of the daily slow slip moment, equivalent to that of a MW 5.0 to 5.1 earthquake. By combining the RTR moments with the spatial extents suggested by tremor, we estimate that a typical RTR has peak slip of roughly one‐sixth of the peak slip in the main slow slip event, near‐front slip rate of a few to ten times the main front slip rate, stress drop around half the main event stress drop, and strain energy release rate around one‐tenth that of the main front. Our observations support a picture of RTRs as aseismic subevents with high slip rates but modest strain energy release. RTRs appear to contribute to but not dominate the overall slow slip moment, though they may accommodate most of the slip in certain locations.

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“…These indicate that tremors can occur in a wide range of tectonic environments. Tremors may also be triggered by seismic waves or earth tides (Ghosh et al, ; Miyazawa et al, ; Nakata et al, ; Z. Peng et al, , ; Rubinstein et al, ; Shelly et al, ) and exhibit migrating activity (Bartlow et al, ; Ghosh et al, , ; Houston et al, ; Ide, ; Kao et al, ; Obara et al, ; Obara & Sekine, ; Y. Peng & Rubin, ; Shelly, ; Ueno et al, ; Yamashita et al, ). Furthermore, tremors have been detected prior to some earthquakes (e.g., Shelly, ), and ETS is usually thought to promote loading at the locked segments of the plate interface, which may increase the earthquake risk.…”

Section: Introductionmentioning

confidence: 99%

Laboratory Observations of Tremor‐Like Events Generated During Preslip

Zhuo

Liu

Chen

et al. 2018

Geophysical Research Letters

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The origins of tremors and their relation to fault slip and impending earthquakes remain unclear. Laboratory studies on tremor‐like acoustic emission events generated during preslip may shed some light on the above issues. We conducted stick‐slip experiments and observed tremor‐like events and preslip in the laboratory. The results show the following. (1) The dominant frequency of tremor‐like events increases with accelerating preslip. (2) The evolution of tremor‐like events is spatiotemporally consistent with that of preslip. (3) Interactions between preslip and high‐frequency events indicate the formation of a positive feedback effect between the expansion of preslip and failure of asperities, which leads to stick‐slip instability. Thus, we propose that tremors may be caused by stress variations derived from asperity interactions along fault surfaces at dry conditions. The increasing dominant frequency of tremors may imply the accelerating preslip of an upcoming earthquake.

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

Cited by 24 publications

References 46 publications

Evidence for a scale‐limited low‐frequency earthquake source process

Evidence for a scale‐limited low‐frequency earthquake source process

Variations in slow slip moment rate associated with rapid tremor reversals in Cascadia

Laboratory Observations of Tremor‐Like Events Generated During Preslip

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