Slow slip near the trench at the Hikurangi subduction zone, New Zealand

Wallace, Laura; Webb, Spahr C.; Ito, Yoshihiro; Mochizuki, Kimihiro; Hino, Ryota; Henrys, S. A.; Schwartz, S. Y.; Sheehan, A. F.

doi:10.1126/science.aaf2349

Cited by 283 publications

(532 citation statements)

References 43 publications

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“…SSE slip near Gisborne predominantly occurs beneath the offshore region, with the downdip limit of slip near the coastline, and the SSEs appear to rupture similar areas of the interface repeatedly . A recent seafloor geodetic experiment has shown that slow slip occurs to within at least 2 km of the seafloor beneath the Expedition 375 drilling transect, and it is possible that slow slip continues all the way to the trench (Wallace et al, 2016).…”

Section: Geological Settingmentioning

confidence: 99%

“…These rocks comprise the protolith and reveal the initial conditions for fault rocks that are transported into the SSE source zone at greater depth. In the case of the shallow fault zone, these materials may in fact host SSEs if the events propagate to the trench (e.g., Wallace et al, 2016 To achieve this goal, characterization of the incoming stratigraphy and upper oceanic basement rocks, together with the shallow, most active strand of the frontal thrust system, is essential. This characterization involves a combination of coring, downhole measurements, and logging at proposed Sites HSM-13B, HSM-08A, and HSM-18A, followed by a strategy of carefully coordinated sampling and postexpedition laboratory analyses (e.g., Screaton et al, 2009;Underwood et al, 2010).…”

Section: Scientific Objectivesmentioning

confidence: 99%

“…The CORK at proposed Site HSM-01A involves a simpler design ( Figure F5) with two levels of formation pressure sensing and a distributed string of MTLs. Both CORKs will have pressure sensing at the wellhead to provide a seafloor reference for the downhole pressure sensors; the wellhead sensors will also provide critical data to resolve pressure changes due to vertical deformation of the seafloor during SSEs (e.g., Wallace et al, 2016). LWD acquired during Expedition 372 at proposed Sites HSM-01A and HSM-18A will be used in combination with coring results from those sites to identify target zones for observatory monitoring.…”

Section: Objective 3: Monitor Deformation Hydrogeology and Chemistrmentioning

confidence: 99%

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2017

International Ocean Discovery Program Scientific Prospectus

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Section: Geological Settingmentioning

confidence: 99%

Section: Scientific Objectivesmentioning

confidence: 99%

Section: Objective 3: Monitor Deformation Hydrogeology and Chemistrmentioning

confidence: 99%

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2017

International Ocean Discovery Program Scientific Prospectus

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“…SSEs occur near Gisborne beneath the offshore region, with the downdip limit of slip near the coastline and repeated SSE rupture of the same areas of the interface . A recent seafloor geodetic experiment has shown that slow slip occurs to within 2 km of the seafloor beneath the outer part of the proposed drilling transect, and possibly continues all the way to the trench ( Figure F4) (Wallace et al, 2016).…”

Section: Slow Slip Events On the Hikurangi Subduction Marginmentioning

confidence: 99%

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Barnes¹,

Pecher²,

LeVay³

2017

International Ocean Discovery Program Scientific Prospectus

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International Ocean Discovery Program (IODP) Expedition 372 combines two research topics, slow slip events (SSEs) on subduction faults and actively deforming gas hydrate-bearing landslides (Proposal 841-APL). Our study area on the Hikurangi margin east of New Zealand provides unique locations for addressing both research topics.Gas hydrates have long been suspected of being involved in seafloor failure; not much evidence, however, has been found to date for gas hydrate-related submarine landslides. Solid, icelike gas hydrate in sediment pores is generally thought to increase seafloor strength, as confirmed by a number of laboratory measurements. Dissociation of gas hydrate to water and overpressured gas, on the other hand, may destabilize the seafloor, potentially causing submarine landslides.The Tuaheni Landslide Complex on the Hikurangi margin shows evidence for active, creeping deformation. Intriguingly, the landward edge of creeping coincides with the pinchout of the base of gas hydrate stability (BGHS) on the seafloor. We therefore hypothesize that gas hydrate may be linked to creeping by (1) repeated small-scale sliding at the BGHS, in a variation of the conventional model linking gas hydrates and seafloor failure; (2) overpressure at the BGHS due to a permeability reduction linked to gas hydrates, which may lead to hydrofracturing, weakening the seafloor and allowing transmission of pressure into the gas hydrate stability zone; or (3) icelike viscous deformation of gas hydrates in sediment pores, similar to onshore rock glaciers. The latter two processes imply that gas hydrate itself is involved in creeping, constituting a paradigm shift in relating gas hydrates to submarine slope failure. Alternatively, creeping may not be related to gas hydrates but instead be caused by repeated pressure pulses or linked to earthquake-related liquefaction. We have devised a coring and logging program to test our hypotheses.SSEs at subduction zones are an enigmatic form of creeping fault behavior. At the northern Hikurangi subduction margin (HSM), they are among the best-documented and shallowest on Earth. They recur about every 2 y and may extend close to the trench, where clastic and pelagic sediments about 1.0-1.5 km thick overlie the subducting, seamount-studded Hikurangi Plateau. The northern HSM thus provides an excellent setting to use IODP capabilities to discern the mechanisms behind slow slip fault behavior, as proposed in IODP Proposal 781A-Full.The objectives of Proposal 781A-Full will be implemented across two related IODP expeditions, 372 and 375. Expedition 372 will undertake logging while drilling (LWD) at three sites targeting the upper plate (midslope basin, proposed Site HSM-01A), the frontal thrust (proposed Site HSM-18A), and the subducting section in the trench (proposed Site HSM-05A). Expedition 375 will undertake coring at the same sites, as well as an additional seamount site on the subducting plate, and implement the borehole observatory objectives. The data from each expedition will be...

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“…, even though some happen at shallow depth, notably in New Zealand [4][5][6] and Costa Rica 7,8 . Slow-slip events at subduction zones worldwide often embody similar, characteristic features [9][10][11][12][13] .…”

mentioning

confidence: 99%

Slow-slip events in semi-brittle serpentinite fault zones

Goswami¹,

Barbot²

2018

Preprint

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Slow-slip events are earthquake-like events only with much lower slip rates. While peak coseismic velocities can reach tens of meters per second, slow-slip is on the order of 10 −7±2 m/s and may last for days to weeks. Under the rate-and-state model of fault friction, slow-slip is produced only when the asperity size is commensurate with the critical nucleation size, a function of frictional properties. However, it is unlikely that all subduction zones embody the same frictional properties. In addition to friction, plastic flow of antigorite-rich serpentinite may significantly influence the dynamics of fault slip near the mantle wedge corner. Here, we show that the range of frictional parameters that generate slow slip is widened in the presence of a serpentinized layer along the subduction plate interface. We observe increased stability and damping of fast ruptures in a semi-brittle fault zone governed by both brittle and viscoelastic constitutive response. The rate of viscous serpentinite flow, governed by dislocation creep, is enhanced by high ambient temperatures. When effective viscosity is taken to be dynamic, long-term slow slip events spontaneously emerge. Integration of rheology, thermal effects, and other microphysical processes with rate-and-state friction may yield further insight into the phenomenology of slow slip.The dynamics of fault slip at subduction zones can assume a wide range of behaviors. A continuum of slip modes that includes fast earthquakes, slow-slip events, and stable creep determines seismic hazards 1,2 . Along the megathrust, earthquakes, very low frequency earthquakes, and tsunami earthquakes are typically found updip of the continental Mohorovicic (Moho) discontinuity. In contrast, slow-slip events are often found close to or below the continental Moho depth at many subduction zones around the circum-Pacific seismic belt 3 , even though some happen at shallow depth, notably in New Zealand 4-6 and Costa Rica 7,8 . Slow-slip events at subduction zones worldwide often embody similar, characteristic features [9][10][11][12][13] . In particular, we observe small stress drops in the range 10-200 kPa, short recurrence times of a few months to a few years, and sometimes more regular periodicity than for earthquakes 14 . Some characteristics of slow-slip events can be explained within the context of rate-and-state friction 15,16 with conditionally stable behavior [17][18][19][20][21] . Runaway frictional instabilities require a critical size for nucleation that depends on the frictional parameters and the effective confining pressure. For sufficiently small velocity-weakening asperities, only creep spontaneously occurs. Slow-slip events emerge spontaneously when the asperity size is commensurate to critical nucleation size 22 . As slow-slip events are now found close to universally at subduction zones [23][24][25][26][27][28] , it is unrealistic to expect the same combination of parameters across widely distant regions (Fig. 1A). Several authors developed and investigated other friction l...

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Slow slip near the trench at the Hikurangi subduction zone, New Zealand

Cited by 283 publications

References 43 publications

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Slow-slip events in semi-brittle serpentinite fault zones

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