Initiation of Strike‐Slip Faults, Serpentinization, and Methane: The Nootka Fault Zone, the Juan de Fuca‐Explorer Plate Boundary

Abstract An historically unprecedented seismic moment was released by crustal events of the 2019–2020 earthquake sequence near southwest Puerto Rico. The sequence involved at least two, and perhaps three interacting fault systems. The largest Mw 6.4 event was likely triggered by left lateral strike-slip events along the eastern extension of the North Boquerón Bay-Punta Montalva fault zone. The mainshock occurred in a normal fault zone that extends into a region where previous studies documented extensional deformation, beyond the Ponce fault and the Bajo Tasmanian fault. Coulomb stress changes by the mainshock may have triggered further normal-faulting aftershocks, left lateral strike-slip events in the region where these two fault zones interacted, and possibly right lateral strike-slip aftershocks along a third structure extending southward, the Guayanilla fault zone. Extension directions of the seismic sequence are consistently north-northwest–south-southeast-oriented, in agreement with the Global Navigation Satellite Systems-inferred motion direction of eastern Hispaniola relative to western Puerto Rico, and with crustal stress estimates for the overriding plate boundary zone.

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Focused Fluid Flow Along the Nootka Fault Zone and Continental Slope, Explorer‐Juan de Fuca Plate Boundary

Geochemistry Geophysics Geosystems ◽

10.1029/2020gc009095 ◽

2020 ◽

Vol 21 (8) ◽

Author(s):

M. Riedel ◽

K. M. M. Rohr ◽

G. D. Spence ◽

D. Kelley ◽

J. Delaney ◽

...

Keyword(s):

Fluid Flow ◽

Continental Slope ◽

Fault Zone ◽

Plate Boundary ◽

Juan De Fuca Plate ◽

Juan De Fuca

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Deformation of continental blocks within convergent plates: Anatolia as a case study

10.5194/egusphere-egu2020-18856 ◽

2020 ◽

Author(s):

Cengiz Zabcı ◽

Taylan Sançar ◽

Müge Yazıcı ◽

Anke M. Friedrich ◽

Naki Akçar

Keyword(s):

Fault Zone ◽

Plate Boundary ◽

Slip Rate ◽

Shear Zones ◽

Strike Slip ◽

Central Anatolia ◽

Western Boundary ◽

The West ◽

Secondary Importance ◽

Continental Block

Anatolia is part of the west-central Alpide plate-boundary zone, particularly where the deformation is characterized by the westward extrusion of this continental block between the Arabian-Eurasian collision in the east and the Hellenic Subduction in the west. Although, this motion mostly happens along the boundary structures, i.e., the North Anatolian and East Anatolian shear zones, there are multiple studies documenting the active deformation along NE-striking sinistral and NW-striking dextral strike-slip faults within the central and eastern parts of Anatolia. These secondary faults slice Anatolia into several pieces giving formation of the Malatya-Erzincan, Cappadocian and Central Anatolian slices from east to west, where their boundary geometries are strongly controlled by the weak zones, the Tethyan Suture Zones.We compiled all geological slip-rate and palaeoseismological studies, which point out inhomogeneous magnitude of deformation along different sections of these secondary structures. The Central Anatolian Fault Zone, the westernmost NE-striking sinistral strike-slip structure and the western boundary between the Central Anatolia and Cappadocian slices, has an average horizontal slip-rate of about 1 to 1.5 mm/a for the last few tens of thousands of years. The earthquake recurrence of about 4500 years between two events revealed on the northern sections of the CAFZ also support this rate of deformation. However, the Malatya-Ovac&#305;k Fault Zone has a bimodal behaviour in terms of deformation rate, which is 2.5 times higher along its northern member, the Ovac&#305;k Fault (OF) than the southern one, the Malatya Fault (MF) (2.5 to 1 mm/a), respectively. This velocity difference between two distinct members of the same fault zone can be explained by the relative westward motion of slices where the OF makes the direct contact between the Central Anatolian and Malatya-Erzincan, and the MF delimits Cappadocian and Malatya-Erzincan slices. Although these structures, which are shallow and probably deform only the upper crust, are of having secondary importance, yet they are still capable of producing infrequent but strong earthquakes within this highly deforming convergent setting. This study is supported by T&#220;B&#304;TAK projects no. 114Y227 and 114Y580.

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The Septentrional–Oriente strike-slip Fault Zone: polyphase deformation and fault strand switching in the Northern Caribbean plate boundary (Windward Passage)

10.5194/egusphere-egu21-5512 ◽

2021 ◽

Author(s):

Alana Oliveira de Sa ◽

Elia d’Acremont ◽

Sylvie Leroy ◽

Sara Lafuerza

Keyword(s):

Fault Zone ◽

Carbonate Platform ◽

Plate Boundary ◽

Strike Slip ◽

Strike Slip Fault ◽

Caribbean Plate ◽

Oblique Collision ◽

The North ◽

Northern Border ◽

The Caribbean

The northern border of the Caribbean plate is characterized by the oblique collision between the Caribbean and North American tectonic plates. Increasing obliquity of the collision between these two plates lead to complex strike-slip fault zones, which successively jump southward to accommodate the eastward escape of the Caribbean plate and the collisional indentation against the Bahama carbonate platform. The present-day Septentrional&#8211;Oriente Fault zone (SOFZ) defines the northern limit of the Caribbean plate, accommodating much of the obliquity of the convergence. Since its inception, at the end of the Oligocene, the current active style of the strike-slip boundary evolves over time. We focus our study on the Windward Passage area between the south-east of Cuba and the north-west of Haiti coast. Currently crossed by the SOFZ, the tectono-sedimentary framework of this large strait displays critical evidences to constrain the Neogene evolution of the northern boundary of the Caribbean plate. Based on seismic reflection and swath-bathymetric dataset we shed light on the structure and tectonic pattern of the Windward Passage. Our study provides structural and stratigraphic insights into relative timing of deformation along the Windward Passage and new elements to constrain the southeastward shift of the north Caribbean plate boundary until its present-day position. Contrasts in patterns of deformation on the Windward Passage area reveal a polyphase tectonic history of dominant strike-slip faulting impacted by the rate and obliquity variations of the convergence. Deformation phases recorded by the offshore sedimentary cover in the Windward Passage correlate well with the major paleogeographic reorganization episodes described onland (Late Eocene, Late Oligocene, Middle Miocene and Late Pliocene). A left-lateral shift of at least ~80 km is demonstrated by the restoration of the offset of the seismic units, estimating a Pliocene age for the onset of the SOFZ segments activity in this area.

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The 1918 and 1957 Vancouver Island earthquakes

Bulletin of the Seismological Society of America ◽

10.1785/bssa0780020617 ◽

1988 ◽

Vol 78 (2) ◽

pp. 617-635

Author(s):

John F. Cassidy ◽

Robert M. Ellis ◽

Garry C. Rogers

Keyword(s):

Surface Wave ◽

Fault Zone ◽

Relative Motion ◽

Stress Drop ◽

Seismic Moment ◽

Focal Depth ◽

Vancouver Island ◽

Strike Slip ◽

Lateral Motion ◽

Juan De Fuca

Abstract Since 1918, six significant earthquakes (5.2 < M < 7.2) have occurred in the region of central Vancouver Island where the Juan de Fuca, Explorer, and America plates interact. In this study, two of the largest earthquakes are examined in detail: the 1918 (MS ≃ 7) and the 1957 (MS ≃ 6) events. The preferred location of the 1918 earthquake is on Vancouver Island at 49.44°N, 126.22°W, with a focal depth of 15 km. Magnitudes determined are MS = 6.9 ± 0.3 and mb = 7.2 ± 0.4. Analysis of surface waves suggests this is a predominantly strike-slip earthquake occurring along either a NNW- or an ENE-striking fault. The seismic moment is estimated as 7.40 × 1025 dyne-cm and the stress drop to be 122 bars. The 1957 earthquake has been relocated on the continental shelf west of Vancouver Island at 49.64°N, 127.00°W, with a focal depth of 30 km. Magnitudes determined are MS = 5.9 ± 0.2 and mb = 6.3 ± 0.3. Surface wave and P-nodal analyses indicate that this is a predominantly strike-slip earthquake; either dextral along an NNW-striking fault, or sinistral along a ENE-striking fault. The seismic moment is estimated as 8.14 × 1024 dyne-cm and the stress drop to be 36 bars. The 1918 earthquake appears to be a crustal intraplate event occurring in the lithosphere of the America plate, resulting from the complicated interaction of the Explorer, Juan de Fuca, and America plates. The preferred epicenter, depth, focal mechanism, and stress drop for the 1957 earthquake are consistent with the left-lateral motion between the Juan de Fuca and Explorer plates along the subducted extension of the Nootka fault zone. This earthquake is identical, within uncertainties, to events occurring in 1972 and 1986. We believe that these three earthquakes provide the best definition to date of both the position of the subducting portion of the Nootka fault zone west of Vancouver Island and the direction of relative motion along this fault.

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RHEOLOGIC EVOLUTION OF A CRUSTAL-SCALE STRIKE-SLIP FAULT ZONE: A CASE STUDY OF THE KELLYLAND FAULT ZONE IN EASTERN MAINE

10.1130/abs/2019ne-328268 ◽

2019 ◽

Author(s):

Walter A. Sullivan ◽

Keyword(s):

Fault Zone ◽

Strike Slip ◽

Strike Slip Fault

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Kinematic partitioning in the Southern Andes (39° S–46° S) inferred from lineament analysis and reassessment of exhumation rates

International Journal of Earth Sciences ◽

10.1007/s00531-021-02068-y ◽

2021 ◽

Author(s):

Paul Leon Göllner ◽

Jan Oliver Eisermann ◽

Catalina Balbis ◽

Ivan A. Petrinovic ◽

Ulrich Riller

Keyword(s):

Fault Zone ◽

Vertical Displacement ◽

Strike Slip ◽

Structural Studies ◽

Southern Andes ◽

Plate Convergence ◽

Exhumation Rates ◽

Lineament Analysis ◽

Dextral Strike Slip ◽

Data Call

AbstractThe Southern Andes are often viewed as a classic example for kinematic partitioning of oblique plate convergence into components of continental margin-parallel strike-slip and transverse shortening. In this regard, the Liquiñe-Ofqui Fault Zone, one of Earth’s most prominent intra-arc deformation zones, is believed to be the most important crustal discontinuity in the Southern Andes taking up margin-parallel dextral strike-slip. Recent structural studies, however, are at odds with this simple concept of kinematic partitioning, due to the presence of margin-oblique and a number of other margin-parallel intra-arc deformation zones. However, knowledge on the extent of such zones in the Southern Andes is still limited. Here, we document traces of prominent structural discontinuities (lineaments) from the Southern Andes between 39° S and 46° S. In combination with compiled low-temperature thermochronology data and interpolation of respective exhumation rates, we revisit the issue of kinematic partitioning in the Southern Andes. Exhumation rates are maximal in the central parts of the orogen and discontinuity traces, trending predominantly N–S, WNW–ESE and NE–SW, are distributed across the entire width of the orogen. Notably, discontinuities coincide spatially with large gradients in Neogene exhumation rates and separate crustal domains characterized by uniform exhumation. Collectively, these relationships point to significant components of vertical displacement on these discontinuities, in addition to horizontal displacements known from published structural studies. Our results agree with previously documented Neogene shortening in the Southern Andes and indicate orogen-scale transpression with maximal vertical extrusion of rocks in the center of the transpression zone. The lineament and thermochronology data call into question the traditional view of kinematic partitioning in the Southern Andes, in which deformation is focused on the Liquiñe-Ofqui Fault Zone.

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