Model for the origin of the Yakutat block, an accreting terrane in the northern Gulf of Alaska

Bruns, Terry R.

doi:10.1130/0091-7613(1983)11<718:mftoot>2.0.co;2

Cited by 144 publications

(120 citation statements)

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“…Based on the near-surface tectonic expression, Wang and Hu [2006] and Kimura et al [2008] would characterize this region as the transition zone of subduction between the inner and outer wedge zones that accommodates the bulk of subduction zone shortening. Although the transition zone is typically defined between the outer arc high and continental slope, we suggest that the shallow subduction angle from the buoyant Yakutat slab above the Pacific plate changes the subduction and splay fault geometry [e.g., Bruns, 1983;Brocher et al, 1994;Eberhart-Phillips et al, 2006;Fuis et al, 2008], pushes this transition zone closer to mainland Alaska for the PWS asperity, and provides the buoyancy to form the barrier islands of PWS. Assuming Montague Island defines a region of coseismic strengthening at the outer arc high and the trailing edge of the Yakutat terrane provides midcrustal heterogeneities and/or duplexing for splays to diverge from the megathrust, we outline an area with the maximum plate coupling where the faults will coseismically rupture during most great earthquakes (Figure 6).…”

Section: Subduction Zone Structural Domains and Asperity Focusmentioning

confidence: 99%

“…West of Montague Island, the subducting Yakutat slab is absent and the Pacific Plate subducts directly beneath the North American plate [e.g., Brocher et al, 1994;EberhartPhillips et al, 2006]. The PWS asperity, defined as a region of high moment release [e.g., Lay et al, 1982;Scholz and Campos, 2012], was centered beneath the southwest end of Montague Island near a prominent magnetic high that defines the western boundary of the subducted Yakutat terrane (Figure 1) [Bruns, 1983;Griscom and Sauer, 1990;Brocher et al;1994;Johnson et al, 1996;Zweck et al, 2002;Eberhart-Phillips et al, 2006].…”

Section: Introductionmentioning

confidence: 99%

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Megathrust splay faults at the focus of the Prince William Sound asperity, Alaska

et al. 2013

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[1] High-resolution sparker and crustal-scale air gun seismic reflection data, coupled with repeat bathymetric surveys, document a region of repeated coseismic uplift on the portion of the Alaska subduction zone that ruptured in 1964. This area defines the western limit of Prince William Sound. Differencing of vintage and modern bathymetric surveys shows that the region of greatest uplift related to the 1964 Great Alaska earthquake was focused along a series of subparallel faults beneath Prince William Sound and the adjacent Gulf of Alaska shelf. Bathymetric differencing indicates that 12 m of coseismic uplift occurred along two faults that reached the seafloor as submarine terraces on the Cape Cleare bank southwest of Montague Island. Sparker seismic reflection data provide cumulative Holocene slip estimates as high as 9 mm/yr along a series of splay thrust faults within both the inner wedge and transition zone of the accretionary prism. Crustal seismic data show that these megathrust splay faults root separately into the subduction zone décollement. Splay fault divergence from this megathrust correlates with changes in midcrustal seismic velocity and magnetic susceptibility values, best explained by duplexing of the subducted Yakutat terrane rocks above Pacific plate rocks along the trailing edge of the Yakutat terrane. Although each splay fault is capable of independent motion, we conclude that the identified splay faults rupture in a similar pattern during successive megathrust earthquakes and that the region of greatest seismic coupling has remained consistent throughout the Holocene.

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Section: Subduction Zone Structural Domains and Asperity Focusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Megathrust splay faults at the focus of the Prince William Sound asperity, Alaska

et al. 2013

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“…Generalized tectonic setting of the Alaskan orocline. Normal subduction of the Pacific Plate beneath the Aleutian Arc transitions eastward to collision of the Yakutat block with the elbow area of southeastern Alaska (YB; ongoing since the Miocene [e.g., Lahr and Plafker, 1980;Bruns, 1983]). Large semicircular arrow schematically shows rotation of south-central Alaska [after Fletcher, 2002].…”

Section: A312 Kuril Basin and Sea Of Okhotskmentioning

confidence: 99%

Collisional model for rapid fore‐arc block rotations, arc curvature, and episodic back‐arc rifting in subduction settings

Wallace

Ellis

Mann

2009

Geochem Geophys Geosyst

102

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[1] We review geophysical and geological data from 23 active and ancient plate boundaries to document a compelling spatial and temporal relationship between collision, plate boundary curvature, rapid tectonic rotations, and the occurrence of back-arc rifting. Our observations support a conceptual model where the change from subduction to collision causes rapid fore-arc rotation (when viewed in a reference frame relative to the bounding tectonic plates), leading to marked plate boundary curvature. Our global compilation reveals that most active back-arc rifts are associated with rapidly rotating fore arcs and nearby collisions. Thus, we propose that collision and rapid fore-arc rotations play a major role in the evolution and kinematics of back-arc basins. We conduct numerical modeling to better understand the physical processes behind these observed rapid tectonic rotations at convergent margins. Our results suggest that the presence of an indentor or choke point in the subduction system (e.g., collision) can generate rapid rotation of the fore arc about a nearby pole and lead to back-arc rifting. The rate of fore-arc rotation and back-arc rifting depends on the incoming indentor velocity and can be greatly enhanced by slab rollback and the presence of a low-viscosity back arc. Where viscosity of the back arc is low, fore-arc rotation dominates; where back-arc viscosity is high, the formation of strike-slip faults and tectonic escape dominates. Our observational and model-derived results illustrate that shallow crustal forces produced by the entry of buoyant features into subduction zones are a fundamental mechanism for the generation of fore-arc block rotations, plate boundary curvature, back-arc rift evolution, and tectonic escape in subduction systems. Rollback of the subducting slab within the mantle will certainly enhance the processes we describe but it is not the only driving force. Wallace, L. M., S. Ellis, and P. Mann (2009), Collisional model for rapid fore-arc block rotations, arc curvature, and episodic back-arc rifting in subduction settings, Geochem. Geophys. Geosyst., 10, Q05001,

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“…This series of faults has moved repeatedly to form the Pamplona spur, an offshore bathymetric high (Figure 2). Four to ten kilometers of convergence has occurred across these faults in the Pleistocene [Bruns, 1983;Pfiaker, 1987 determined focal mechanisms for the largest event and an aftershock on April 19 from P wave first motions and S wave polarization data. Their results (Table 1) …”

mentioning

confidence: 99%

Earthquakes in the Pamplona zone, Yakutat block, south central Alaska

Doser¹,

Pelton

Veilleux

1997

J. Geophys. Res.

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Model for the origin of the Yakutat block, an accreting terrane in the northern Gulf of Alaska

Cited by 144 publications

References 0 publications

Megathrust splay faults at the focus of the Prince William Sound asperity, Alaska

Megathrust splay faults at the focus of the Prince William Sound asperity, Alaska

Collisional model for rapid fore‐arc block rotations, arc curvature, and episodic back‐arc rifting in subduction settings

Earthquakes in the Pamplona zone, Yakutat block, south central Alaska

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