Seismic velocity structure and anisotropy of the Alaska subduction zone based on surface wave tomography

Wang, Yun; Tape, Carl

doi:10.1002/2014jb011438

Cited by 63 publications

(109 citation statements)

References 112 publications

(212 reference statements)

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“…Previous studies estimating Moho depth (Ferris et al, 2003;Brennan et al, 2011;Wang and Tape, 2014) suggest that the offset of the Moho is located 30km north of the main trace of the Denali fault, perhaps along the Hines Creek fault which has been interpreted as the northernmost boundary of the WCT-YCT suture zone (Wahrhaftig et al, 1975). To test the relative importance of the Hines Creek fault in terms of velocity contrast, we repeat the 1D model analysis (grid points shown in Fig.…”

Section: Deep and Shallow Velocity Contrastsmentioning

confidence: 98%

“…Body-wave tomographic studies using local earthquakes (Kissling and Lahr, 1991;Eberhart-Phillips et al, 2006) and teleseismic earthquakes (Qi et al, 2007;MartinShort et al, 2016) have successfully imaged slab structure that is consistent with the WadatiBenioff seismicity patterns. Teleseismic surface-wave wave tomography (Wang & Tape, 2014) of the entire state employed ~50km horizontal cells to image upper mantle structure. Surfacewave phase velocity maps derived from ambient noise show crustal variations, including a possible contrast across the Denali fault (Ward, 2015).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

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Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves

et al. 2017

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Please cite this article as: A.A. Allam, V. Schulte-Pelkum, Y. Ben-Zion, C. Tape, N. Ruppert, Z.E. Ross , Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves, Tectonophysics (2017Tectonophysics ( ), doi: 10.1016Tectonophysics ( /j.tecto.2017 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.A C C E P T E D M A N U S C R I P T AbstractWe examine the structure of the Denali fault system in the crust and upper mantle using double-difference tomography, P-wave receiver functions, and analysis (spatial distribution and moveout) of fault zone head waves. The three methods have complementary sensitivity; tomography is sensitive to 3D seismic velocity structure but smooths sharp boundaries, receiver functions are sensitive to (quasi) horizontal interfaces, and fault zone head waves are sensitive to (quasi) vertical interfaces. The results indicate that the Mohorovičić discontinuity is vertically offset by 10 to 15km along the central 600km of the Denali fault in the imaged region, with the northern side having shallower Moho depths around 30km. An automated phase picker algorithm is used to identify ~1400 events that generate fault zone head waves only at near-fault stations.At shorter hypocentral distances head waves are observed at stations on the northern side of the fault, while longer propagation distances and deeper events produce head waves on the southern side. These results suggest a reversal of the velocity contrast polarity with depth, which we confirm by computing average 1D velocity models separately north and south of the fault. Using teleseismic events with M>=5.1, we obtain 31,400 P receiver functions and apply common- km to the north. To the east, this offset follows the Totschunda fault, which ruptured during the M7.9 2002 earthquake, rather than the Denali fault itself. The combined results suggest that the Denali fault zone separates two distinct crustal blocks, and that the Totschunda and Hines Creeks segments are important components of the fault and Cretaceous-aged suture zone structure.

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Section: Deep and Shallow Velocity Contrastsmentioning

confidence: 98%

Section: Accepted Manuscriptmentioning

confidence: 99%

Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves

et al. 2017

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“…In the past two decades many researchers have investigated the 3-D crustal and upper mantle structure of the Alaska subduction zone using various seismological methods, revealing the high-V subducting Pacific slab and low-V anomalies in the crust and upper-mantle wedge associated with the arc magmatism (for details, see Tian and Zhao, 2012a;Wang and Tape, 2014). Tian and Zhao (2012a) determined Vp and Vs tomography and 3-D P-wave azimuthal anisotropy of the Alaska subduction zone using arrival times of local shallow and intermediate-depth earthquakes recorded by the dense seismic network deployed in South-Central Alaska (Fig.…”

Section: Alaskamentioning

confidence: 99%

“…Teleseismic Rayleigh waves were used to image large-scale variations in Vs structure and anisotropy beneath South-Central Alaska (Wang and Tape, 2014). Their imaging technique employs a twoplane wave representation with finite-frequency sensitivity kernels.…”

Section: Alaskamentioning

confidence: 99%

Seismic anisotropy tomography: New insight into subduction dynamics

2016

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Body-wave and surface-wave tomography, receiver-function imaging, and shear-wave splitting measurements have shown that seismic anisotropy and heterogeneity coexist in all parts of subduction zones, providing important constraints on the mantle flow and subduction dynamics. P-wave anisotropy tomography is a new but powerful tool for mapping three-dimensional variations of azimuthal and radial seismic anisotropy in the crust and mantle. P-wave azimuthal-anisotropy tomography has been applied widely to the Circum-Pacific subduction zones, Mainland China and North America, whereas P-wave radial-anisotropy tomography was applied to only a few areas including Northeast Japan, Southwest Japan and North China Craton. These studies have revealed complex anisotropy in the crust and mantle lithosphere associated with the surface geology and tectonics, anisotropy reflecting subduction-driven corner flow in the mantle wedge, frozen-in fossil anisotropy in the subducting slabs formed at the mid-ocean ridge, as well as olivine fabric transitions due to changes in water content, stress and temperature. Shear-wave splitting tomography methods have been also proposed, but their applications are still limited and preliminary. There is a discrepancy between the surface-wave and body-wave tomographic models in radial anisotropy of the mantle wedge beneath Japan, which is a puzzle but an intriguing topic for future studies.

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“…Upon closer examinations, the deeper part of the YAK has been found to have in the Cook Inlet region a pronounce WSW maximum compression plunging 40 to 60 degrees [84], which was originally considered incorrectly as the PAC. Even deep "shear wave splitting" investigations indicate two pronounced compressional fast directions in this region, one WSW and the other NNW [83,[85][86][87][88]. Also, the stress field throughout most of the Aleutian volcanic arc has been recognized by using volcanic edifice orientations; but, such recognition was not possible for the Cook Inlet region [89] due to the lack of any one prominent edifice orientation.…”

Section: Two Independently Subducting Platesmentioning

confidence: 97%

The Active Yakutat (Kula?) Plate and Its Southcentral Alaska Megathrust and Intraplate Earthquakes

Reeder¹

2016

JEASE

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Alaska geology and plate tectonics have not been well understood due to an active Yakutat plate, believed to be part of the remains of an ancient Kula plate, not being acknowledged to exist in Alaska. It is positioned throughout most of southcentral Alaska beneath the North American plate and above the NNW subducting Pacific plate. The Kula? plate and its eastern spreading ridge were partially "captured" by the North American plate in the Paleocene. Between 63 Ma and 32 Ma, large volumes of volcanics erupted from its subducted N-S striking spreading ridge through a slab window. The eruptions stopped at 32 Ma, likely due to the Pacific plate flat-slab subducting from the south beneath this spreading ridge. At 28 Ma, magmatism started again to the east; indicating a major shift to the east of this "refusing to die" spreading ridge. The captured Yakutat plate has also been subducting since 63 Ma to the WSW. It started to change to WSW flat-slab subduction at 32 Ma, which stopped all subduction magmatism in W and SW Alaska by 22 Ma. The Yakutat plate subduction has again increased with the impact/joining of the coastal Yakutat terrane from the ESE about 5 Ma, resulting in the Cook Inlet Quaternary volcanism of southcentral Alaska. During the 1964 Alaska earthquake, sudden movements along the southcentral Alaska thrust faults between the Yakutat plate and the Pacific plate occurred. Specifically, the movements consisted of the Pacific plate moving NNW under the buried Yakutat plate and of the coastal Yakutat terrane, which is considered part of the Yakutat plate, thrusting WSW onto the Pacific plate. These were the two main sources of energy release for the E part of this earthquake. Only limited movement between the Yakutat plate and the North American plate occurred during this 1964 earthquake event. Buried paleopeat age dates indicate the thrust boundary between the Yakutat plate and North American plate will move in about 230 years, resulting in a more "continental" type megathrust earthquake for southcentral Alaska. There are, therefore, at least two different types of megathrust earthquakes occurring in southcentral Alaska: the more oceanic 1964 type and the more continental type. In addition, large "active" WSW oriented strike-slip faults are recognized in the Yakutat plate, called slice faults, which represent another earthquake hazard for the region. These slice faults also indicate important oil/gas and mineral resource locations.

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Seismic velocity structure and anisotropy of the Alaska subduction zone based on surface wave tomography

Cited by 63 publications

References 112 publications

Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves

Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves

Seismic anisotropy tomography: New insight into subduction dynamics

The Active Yakutat (Kula?) Plate and Its Southcentral Alaska Megathrust and Intraplate Earthquakes

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