The Dellwood knolls and their role in triple junction tectonics off northern Vancouver Island

1980 ◽  
Vol 17 (5) ◽  
pp. 577-593 ◽  
Author(s):  
R. P. Riddihough ◽  
R. G. Currie ◽  
R. D. Hyndman
Keyword(s):  
Triple Junction ◽  
Plate Tectonics ◽  
Vancouver Island ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Geological Evidence ◽  
Topographic Features ◽  
Narrow Valley ◽  
The Pacific ◽  
Geophysical Surveys

The Dellwood knolls are two small topographic features on the ocean floor off northern Vancouver Island. They have been proposed as a spreading centre connecting the Explorer ridge to the Queen Charlotte fault and the location of a triple junction between the Pacific, American, and Juan de Fuca plate systems.Detailed geophysical surveys and ocean-bottom seismometer deployments confirm that they are the site of active seismicity and recent volcanism. Modelling of the magnetic anomaly field shows that it is almost entirely produced by normally magnetized material, supporting geological evidence that the knolls are probably less than 1 Ma old. Although the two knolls are separated by a narrow valley with some downfaulting, they do not form a clearly linear spreading rift.Assessment of their role in the plate tectonics of the region suggests that spreading at the knolls was initiated around 1 Ma ago in crust now 4.5 Ma old as part of a complex, northwesterly ridge migration process at the northern end of the Explorer ridge. Reconstruction of this process, which involves asymmetric spreading and ridge jumping, provides an explanation for the creation of the associated Paul Revere and Winona ridges.

Seismically Derived Ground Tilts Related to the 2010 Chilean Tsunami

2021 ◽  
Author(s):  
Jui-Chun Freya Chen ◽  
Wu-Cheng Chi ◽  
Chu-Fang Yang
Keyword(s):  
Deep Ocean ◽  
Propagation Model ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Tsunami Propagation ◽  
Ground Tilt ◽  
Tsunami Waves ◽  
The Pacific ◽  
Seismic Networks ◽  
Back Azimuth

Abstract Developing new ways to observe tsunami contributes to tsunami research. Tidal and deep-ocean gauges are typically used for coastal and offshore observations. Recently, tsunami-induced ground tilts offer a new possibility. The ground tilt signal accompanied by 2010 Mw 8.8 Chilean earthquake were observed at a tiltmeter network in Japan. However, tiltmeter stations are usually not as widely installed as broadband seismometers in other countries. Here, we studied broadband seismic records from Japan’s F-net and found ground tilt signals consistent with previously published tiltmeter dataset for this particular tsunamic event. Similar waveforms can also be found in broadband seismic networks in other countries, such as Taiwan, as well as an ocean-bottom seismometer. We documented a consistent time sequence of evolving back-azimuth directions of the tsunami waves at different stages of tsunami propagation through beamforming-frequency–wavenumber analysis and particle-motion analysis; the outcomes are consistent with the tsunami propagation model provided by the Pacific Tsunami Warning Center. These results shown that dense broadband seismic networks can provide a useful complementary dataset, in addition to tiltmeter arrays and other networks, to study or even monitor tsunami propagation using arrayed methods.

scholarly journals Precise aftershock distribution of the 2011 off the Pacific coast of Tohoku Earthquake revealed by an ocean-bottom seismometer network

2012 ◽  
Vol 64 (12) ◽  
pp. 1137-1148 ◽  
Author(s):  
Masanao Shinohara ◽  
Yuya Machida ◽  
Tomoaki Yamada ◽  
Kazuo Nakahigashi ◽  
Takashi Shinbo ◽  
...  
Keyword(s):  
Pacific Coast ◽  
Tohoku Earthquake ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Aftershock Distribution ◽  
The Pacific ◽  
Precise Aftershock Distribution

scholarly journals Aftershock observation of the 2011 off the Pacific coast of Tohoku Earthquake by using ocean bottom seismometer network

2011 ◽  
Vol 63 (7) ◽  
pp. 835-840 ◽  
Author(s):  
Masanao Shinohara ◽  
Tomoaki Yamada ◽  
Kazuo Nakahigashi ◽  
Shin’ichi Sakai ◽  
Kimihiro Mochizuki ◽  
...  
Keyword(s):  
Pacific Coast ◽  
Tohoku Earthquake ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
The Pacific ◽  
Aftershock Observation

The Pacific OBS Research into Convecting Asthenosphere (ORCA) Experiment

2021 ◽  
Author(s):  
Zachary C. Eilon ◽  
James B. Gaherty ◽  
Lun Zhang ◽  
Joshua Russell ◽  
Sean McPeak ◽  
...  
Keyword(s):  
Data Quality ◽  
Recovery Rate ◽  
Body Wave ◽  
Spectral Characteristics ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Central Pacific ◽  
Seismic Arrays ◽  
Daily Data ◽  
The Pacific

Abstract The Pacific ocean-bottom seismometer (OBS) Research into Convecting Asthenosphere (ORCA) experiment deployed two 30-station seismic arrays between 2018 and 2020—a US contribution to the international PacificArray project. The “Young ORCA” array deployed on ∼40 Ma central Pacific seafloor had a ∼68% data recovery rate, whereas the “Old ORCA” array deployed on ∼120 Ma southwest Pacific seafloor had a ∼80% recovery rate. We detail here the seismic data quality, spectral characteristics, and engineering challenges of this experiment. We provide information to assist users of this dataset, including OBS orientations and tables of daily data quality for all channels. Preliminary analysis illustrates the utility of these data for surface- and body-wave seismic imaging.

Finite element study of uplift and strain across Vancouver Island

1994 ◽  
Vol 31 (10) ◽  
pp. 1510-1522 ◽  
Author(s):  
Kelin Wang ◽  
Herb Dragert ◽  
H. Jay Melosh
Keyword(s):  
Finite Element ◽  
Surface Deformation ◽  
Viscoelastic Model ◽  
Vancouver Island ◽  
Slip Zone ◽  
Recurrence Time ◽  
Dislocation Model ◽  
Stick Slip ◽  
Geological Evidence ◽  
Geophysical Surveys

Geological evidence for sudden coastal subsidence along the west coast of southern Vancouver Island points to the occurrence of great prehistorical subduction earthquakes. Contemporary uplift and crustal shortening patterns in southern Vancouver Island appear to indicate that the subduction megathrust fault is currently locked. To understand better the dynamics of the observed surface deformation, we develop a finite element model of earthquake cycles for the northern Cascadia subduction zone across southern Vancouver Island, using a linear viscoelastic rheology. The model consists of the continental and oceanic lithospheres, the asthenospheric mantle with a viscosity of 5 × 1019 Pa∙s, and a low-viscosity (1018 Pa∙s) mantle wedge between the subducted oceanic plate and the overlying continental plate. The shallow geometry of the subducted Juan de Fuca plate is well defined by the results of various geophysical surveys, and the deep geometry is constrained by the results of seismic tomography. The model megathrust fault has a stick-slip zone near the surface, a viscoelastically weakly coupled zone (viscosity 7 × 1017 Pa∙s) at depth, and a narrow free-slip zone in between. Earthquakes are allowed to occur every 500 years. Varying the recurrence time does not greatly affect the surface deformation in the later part of the interseismic period. Experiments varying the width of the stick-slip zone lead to the conclusion that a width of about 70 km satisfies both the observed coseismic coastal subsidence and the contemporary surface deformation pattern. The results of a simple elastic dislocation model for thrust earthquakes that had been previously applied to the region are compared with the solutions of the viscoelastic model. Despite its simplicity, the elastic model approximates well the surface deformation of the viscoelastic model in the second half of the interseismic period, although it predicts a slightly narrower stick-slip zone of the fault. The present viscoelastic model is limited principally by the two-dimensional approach, the assumptions of purely stick-slip behaviour of the thrust fault, and the uncertainties in rock rheology.

scholarly journals On the enigmatic birth of the Pacific Plate within the Panthalassa Ocean

2016 ◽  
Vol 2 (7) ◽  
pp. e1600022 ◽  
Author(s):  
Lydian M. Boschman ◽  
Douwe J. J. van Hinsbergen
Keyword(s):  
Triple Junction ◽  
Tectonic Evolution ◽  
Plate Boundary ◽  
Pacific Plate ◽  
Plate Tectonic ◽  
Point Location ◽  
Marine Magnetic Anomalies ◽  
The Pacific ◽  
History Of ◽  
Ridge System

The oceanic Pacific Plate started forming in Early Jurassic time within the vast Panthalassa Ocean that surrounded the supercontinent Pangea, and contains the oldest lithosphere that can directly constrain the geodynamic history of the circum-Pangean Earth. We show that the geometry of the oldest marine magnetic anomalies of the Pacific Plate attests to a unique plate kinematic event that sparked the plate’s birth at virtually a point location, surrounded by the Izanagi, Farallon, and Phoenix Plates. We reconstruct the unstable triple junction that caused the plate reorganization, which led to the birth of the Pacific Plate, and present a model of the plate tectonic configuration that preconditioned this event. We show that a stable but migrating triple junction involving the gradual cessation of intraoceanic Panthalassa subduction culminated in the formation of an unstable transform-transform-transform triple junction. The consequent plate boundary reorganization resulted in the formation of a stable triangular three-ridge system from which the nascent Pacific Plate expanded. We link the birth of the Pacific Plate to the regional termination of intra-Panthalassa subduction. Remnants thereof have been identified in the deep lower mantle of which the locations may provide paleolongitudinal control on the absolute location of the early Pacific Plate. Our results constitute an essential step in unraveling the plate tectonic evolution of “Thalassa Incognita” that comprises the comprehensive Panthalassa Ocean surrounding Pangea.

The trace of the Pacific-Cocos-Nazca triple junction in the Central Pacific and the formation of an overlapping spreading centre

Terra Nova ◽  
2008 ◽  
Vol 20 (3) ◽  
pp. 246-251 ◽  
Author(s):  
Martin Meschede ◽  
Udo Barckhausen ◽  
Martin Engels ◽  
Wilhelm Weinrebe
Keyword(s):  
Triple Junction ◽  
Central Pacific ◽  
The Pacific

scholarly journals Microearthquake seismicity and focal mechanisms at the Rodriguez Triple Junction in the Indian Ocean using ocean bottom seismometers

2001 ◽  
Vol 106 (B12) ◽  
pp. 30689-30699 ◽  
Author(s):  
Kei Katsumata ◽  
Toshinori Sato ◽  
Junzo Kasahara ◽  
Naoshi Hirata ◽  
Ryota Hino ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Triple Junction ◽  
Focal Mechanisms ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometers ◽  
The Indian Ocean
Sign in / Sign up

Export Citation Format

Share Document