Cascadia Tremor Located Near Plate Interface Constrained by
            <i>S</i>
            Minus
            <i>P</i>
            Wave Times

Rocca, Mario La; Creager, K. C.; Galluzzo, Danilo; Malone, Stephen D.; Vidale, John E.; Sweet, J. R.; Wech, A.

doi:10.1126/science.1167112

Cited by 90 publications

(99 citation statements)

References 20 publications

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“…Also supporting this model are seismic observations from LFEs comprising tremor in Japan [Ide et al, 2007a;Shelly et al, 2006] and polarization analysis in Cascadia [Wech and Creager, 2007] showing a tremor mechanism of reverse-thrusting consistent with slip on the subduction zone plate interface. Tremorcomprising LFEs in both Japan [Shelly et al, 2006] and Cascadia [Brown et al, 2009] as well as S-P wave arrival time differentials in Cascadia [La Rocca et al, 2009] also indicate that tremor occurs on the plate interface, congruent with slow slip. Constraining tremor depths is difficult and perhaps tremor does not always occur on the plate boundary and represents slip or other fluid-related deformation 10 s of km above the plate boundary [Kao et al, 2005;McCausland et al, 2005].…”

Section: Discussionmentioning

confidence: 99%

An earthquake‐like magnitude‐frequency distribution of slow slip in northern Cascadia

Wech

Creager

Houston

et al. 2010

Geophysical Research Letters

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Major episodic tremor and slip (ETS) events with Mw 6.4 to 6.7 repeat every 15 ± 2 months within the Cascadia subduction zone under the Olympic Peninsula. Although these major ETS events are observed to release strain, smaller “tremor swarms” without detectable geodetic deformation are more frequent. An automatic search from 2006–2009 reveals 20,000 five‐minute windows containing tremor which cluster in space and time into 96 tremor swarms. The 93 inter‐ETS tremor swarms account for 45% of the total duration of tremor detection during the last three ETS cycles. The number of tremor swarms, N, exceeding duration τ follow a power‐law distribution N ∝ τ−0.66. If duration is proportional to moment release, the slip inferred from these swarms follows a standard Gutenberg‐Richter logarithmic frequency‐magnitude relation, with the major ETS events and smaller inter‐ETS swarms lying on the same trend. This relationship implies that 1) inter‐ETS slip is fundamentally similar to the major events, just smaller and more frequent; and 2) despite fundamental differences in moment‐duration scaling, the slow slip magnitude‐frequency distribution is the same as normal earthquakes with a b‐value of 1.

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Section: Discussionmentioning

confidence: 99%

An earthquake‐like magnitude‐frequency distribution of slow slip in northern Cascadia

Wech

Creager

Houston

et al. 2010

Geophysical Research Letters

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“…This method relies on the assumption that the tremor arrives at near-vertical incidence so that the P waves are predominantly recorded on the vertical component and the S waves are predominantly on the horizontal component. Using these newly computed S-P times, La Rocca et al (2009) dramatically improve the vertical resolution of tremor locations in Cascadia. For the events that they locate, tremor appears to lie on or very close to the subduction interface.…”

Section: Phase Based Location Methodsmentioning

confidence: 97%

“…As discussed in section "Locating Non-volcanic Tremor" and later in section "Tremor Locations: A Broad Depth Distribution in Some Areas? ", other studies suggest that tremor is being radiated from the plate interface and does not have a large depth distribution (La Rocca et al, 2009;Shelly et al, 2006;Brown et al, in press). Clearly, precisely determining tremor locations is critical for our understanding of the source processes of tremor.…”

Section: The Fluid Flow Model For Non-volcanic Tremormentioning

confidence: 95%

“…La Rocca et al (2009) retrieve S-P times by cross-correlating the vertical component of recordings of tremor against the horizontal components. This method relies on the assumption that the tremor arrives at near-vertical incidence so that the P waves are predominantly recorded on the vertical component and the S waves are predominantly on the horizontal component.…”

Section: Phase Based Location Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Non-volcanic Tremor: A Window into the Roots of Fault Zones

Rubinstein

Shelly

Ellsworth

2009

New Frontiers in Integrated Solid Earth Sciences

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The recent discovery of non-volcanic tremor in Japan and the coincidence of tremor with slow-slip in Cascadia have made earth scientists reevaluate our models for the physical processes in subduction zones and on faults in general. Subduction zones have been studied very closely since the discovery of slow-slip and tremor. This has led to the discovery of a number of related phenomena including low frequency earthquakes and very low frequency earthquakes. All of these events fall into what some have called a new class of events that are governed under a different frictional regime than simple brittle failure. While this model is appealing to many, consensus as to exactly what process generates tremor has yet to be reached. Tremor and related events also provide a window into the deep roots of subduction zones, a poorly understood region that is largely devoid of seismicity. Given that such fundamental questions remain about non-volcanic tremor, slow-slip, and the region in which they occur, we expect that this will be a fruitful field for a long time to come.

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“…A better constraint on the absolute depth of tremor events is provided by the S-P times for events occurring immediately beneath the observation network, as demonstrated by La Rocca et al (2009) in the Cascadia subduction zone. At some stations in Kyushu, P-waves are often visible in the vertical component, while S-waves are dominant in all components.…”

Section: Accurate Estimation Of Tremor Depthsmentioning

confidence: 99%

Repeating deep tremors on the plate interface beneath Kyushu, southwest Japan

Yabe

Ide

2013

Earth Planet Sp

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In the subduction zone south of Kyushu Island, at the western extension of the Nankai subduction zone, southwest Japan, the age of the oceanic crust increases toward the south across the subducting Kyushu-Palau ridge. While tremor activity is very high in Nankai, tectonic tremors have only recently been discovered in Kyushu. In this study, we examined tremors beneath Kyushu using an improved version of the envelope correlation method. In doing so, we distinguished tremors from normal earthquakes and background noise using the criteria of source duration and the spectrum ratio between low and high frequencies. Accurate measurement of S-P times, using cross-correlation between vertical and horizontal seismograms, constrains the tremor depth precisely. Tremor activity is low and within a small region in southern Kyushu, where thick crust of the KyushuPalau ridge is being subducted, at depths between 35 and 45 km (i.e., shallower than intra-slab earthquakes by about 20 km), which is consistent with the location of the plate interface within uncertainties proposed in previous studies. Establishing precise depth estimates for tectonic tremors beneath Kyushu, which results from shear slip along the plate interface, is useful in defining the plate interface within the Nankai subduction zone.

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Cascadia Tremor Located Near Plate Interface Constrained by S Minus P Wave Times

Cited by 90 publications

References 20 publications

An earthquake‐like magnitude‐frequency distribution of slow slip in northern Cascadia

An earthquake‐like magnitude‐frequency distribution of slow slip in northern Cascadia

Non-volcanic Tremor: A Window into the Roots of Fault Zones

Repeating deep tremors on the plate interface beneath Kyushu, southwest Japan

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