scholarly journals Three-dimensional seismic structure of the Mid-Atlantic Ridge (35°N): Evidence for focused melt supply and lower crustal dike injection

2005 ◽  
Vol 110 (B9) ◽  
Author(s):  
Robert A. Dunn ◽  
Vedran Lekić ◽  
Robert S. Detrick ◽  
Douglas R. Toomey
Keyword(s):  
Three Dimensional ◽  
Seismic Structure ◽  
Mid Atlantic Ridge ◽  
Lower Crustal ◽  
Dike Injection

scholarly journals Characteristics of relocated hypocenters of the 2018 M6.7 Hokkaido Eastern Iburi earthquake and its aftershocks with a three-dimensional seismic velocity structure

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Saeko Kita
Keyword(s):  
Seismic Velocity ◽  
Three Dimensional ◽  
Double Difference ◽  
Earthquake Catalog ◽  
Seismic Structure ◽  
Depth Limit ◽  
High Attenuation ◽  
South Central ◽  
Collision Zone ◽  
Hidaka Collision Zone

AbstractI relocated the hypocenters of the 2018 M6.7 Hokkaido Eastern Iburi earthquake and its surrounding area, using a three-dimensional seismic structure, the double-difference relocation method, and the JMA earthquake catalog. After relocation, the focal depth of the mainshock became 35.4 km. As previous studies show, in south-central Hokkaido, the Hidaka collision zone is formed, and anomalous deep and thickened forearc crust material is subducting at depths of less than 70 km. The mainshock and its aftershocks are located at depths of approximately 10 to 40 km within the lower crust of the anomalous deep and thickened curst near the uppermost mantle material intrusions in the northwestern edge of this Hidaka collision zone. Like the two previous large events, the aftershocks of this event incline steeply eastward and appear to be distributed in the deeper extension of the Ishikari-teichi-toen fault zone. The highly inclined fault in the present study is consistent with a fault model by a geodetic analysis with InSAR. The aftershocks at depths of 10 to 20 km are located at the western edge of the high-attenuation (low-Qp) zone. These kinds of relationships between hypocenters and materials are the same as the 1970 and 1982 events in the Hidaka collision zone. The anomalous large focal depths of these large events compared with the average depth limit of inland earthquakes in Japan could be caused by the locally lower temperature in south-central Hokkaido. This event is one of the approximately M7 large inland earthquakes that occurred repeatedly at a recurrence interval of approximately 40 years and is important in the collision process in the Hidaka collision zone.

scholarly journals Seismic Structure of Local Crustal Earthquakes beneath the Zipingpu Reservoir of Longmenshan Fault Zone

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Haiou Li ◽  
Xiwei Xu ◽  
Wentao Ma ◽  
Ronghua Xie ◽  
Jingli Yuan ◽  
...  
Keyword(s):  
Fault Zone ◽  
Three Dimensional ◽  
P Wave ◽  
The Tibetan Plateau ◽  
Seismic Structure ◽  
Infiltration Depth ◽  
Low Velocity ◽  
Longmenshan Fault Zone ◽  
Velocity Models ◽  
Longmenshan Fault

Three-dimensional P wave velocity models under the Zipingpu reservoir in Longmenshan fault zone are obtained with a resolution of 2 km in the horizontal direction and 1 km in depth. We used a total of 8589 P wave arrival times from 1014 local earthquakes recorded by both the Zipingpu reservoir network and temporary stations deployed in the area. The 3-D velocity images at shallow depth show the low-velocity regions have strong correlation with the surface trace of the Zipingpu reservoir. According to the extension of those low-velocity regions, the infiltration depth directly from the Zipingpu reservoir itself is limited to 3.5 km depth, while the infiltration depth downwards along the Beichuan-Yingxiu fault in the study area is about 5.5 km depth. Results show the low-velocity region in the east part of the study area is related to the Proterozoic sedimentary rocks. The Guanxian-Anxian fault is well delineated by obvious velocity contrast and may mark the border between the Tibetan Plateau in the west and the Sichuan basin in the east.

Three-dimensional seismic structure of the lithosphere under Montana Lasa

1976 ◽  
Vol 66 (2) ◽  
pp. 501-524
Author(s):  
Keiiti Aki ◽  
Anders Christoffersson ◽  
Eystein S. Husebye
Keyword(s):  
Generalized Inverse ◽  
Random Medium ◽  
Three Dimensional ◽  
P Wave ◽  
Seismic Structure ◽  
Low Velocity ◽  
Medium Theory ◽  
Velocity Anomaly ◽  
Inversion Techniques ◽  
Teleseismic Events

abstract Using P-wave residuals for teleseismic events observed at the Montana Large Aperture Seismic Array (LASA), we have determined the three-dimensional seismic structure of the lithosphere under the array to a depth of 140 km. The root-mean-square velocity fluctuation was found to be at least 3.2 per cent which may be compared to estimate of ca. 2 per cent based on the Chernov random medium theory. The solutions are given by both the generalized inverse and stochastic inverse methods in order to demonstrate the relative merit of different inversion techniques. The most conspicuous feature of the lithosphere under LASA is a low-velocity anomaly in the central and northeast part of the array siting area with the N60°E trend and persisting from the upper crust to depths greater than 100 km. We interpret this low-velocity anomaly as a zone of weakness caused by faulting and shearing associated with the building of the Rocky Mountains.

Plumbing and architecture of a crustal mineralizing system in the Archean Superior Province, Canada

2021 ◽  
Author(s):  
Eric Roots ◽  
Graham Hill ◽  
Ben M. Frieman ◽  
James A. Craven ◽  
Richard S. Smith ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Spatial Association ◽  
Three Dimensional ◽  
3D Models ◽  
Superior Province ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Abitibi Subprovince ◽  
Lower Crustal

<p>The role of melts and magmatic/metamorphic fluids in mineralization processes is well established. However, the role of crustal architecture in defining source and sink zones in the middle to lower crust remains enigmatic. Integration of three dimensional magnetotelluric (MT) modelling and seismic reflection data across the Archean Abitibi greenstone belt of the Superior Province, Canada, reveals a ‘whole-of-crust’ mineralizing system and highlights the controls by crustal architecture on metallogenetic processes. Electrically conductive conduits in an otherwise resistive upper crust are coincident with truncations and offsets of seismic reflections that are mostly interpreted as major brittle-ductile fault zones. The spatial association between these features and low resistivity zones imaged in the 3D models suggest that these zones acted as pathways through which fluids and melts ascended toward the surface. At mid-crustal levels, these ‘conduit’ zones connect to ~50 km long, north-south striking conductors, and are inferred to represent graphite and/or sulphide deposited from cooling fluids. At upper mantle to lower crustal depths, east-west trending conductive zones dominate and display shallow dips. The upper mantle features are broadly coincident with the surface traces of the major deformation zones with which a large proportion of the gold endowment is associated. We suggest that these deep conductors represent interconnected graphitic zones perhaps augmented by sulphides that are relicts from metamorphic fluid and melt emplacement associated primarily with the later stages of regional deformation.  Thus, from the combined MT and seismic data, we develop a crustal-scale architectural model that is consistent with existing geological and deformational models, providing constraints on the sources for and signatures of fluid and magma emplacement that resulted in widespread metallogenesis in the Abitibi Subprovince.</p>

scholarly journals Seismic structure of an oceanic core complex at the Mid-Atlantic Ridge, 22°19′N

2010 ◽  
Vol 115 (B7) ◽  
Author(s):  
Anke Dannowski ◽  
Ingo Grevemeyer ◽  
Cesar R. Ranero ◽  
Georges Ceuleneer ◽  
Marcia Maia ◽  
...  
Keyword(s):  
Seismic Structure ◽  
Core Complex ◽  
Oceanic Core Complex ◽  
Mid Atlantic Ridge

scholarly journals Three-dimensional geometry of axial magma chamber roof and faults at Lucky Strike volcano on the Mid-Atlantic Ridge

2015 ◽  
Vol 120 (8) ◽  
pp. 5379-5400 ◽  
Author(s):  
Violaine Combier ◽  
Tim Seher ◽  
Satish C. Singh ◽  
Wayne C. Crawford ◽  
Mathilde Cannat ◽  
...  
Keyword(s):  
Magma Chamber ◽  
Three Dimensional ◽  
Lucky Strike ◽  
Mid Atlantic Ridge ◽  
Axial Magma Chamber

Crustal structure and surface zonation of the Canadian Appalachians: implications of deep seismic reflection data

1989 ◽  
Vol 26 (2) ◽  
pp. 305-321 ◽  
Author(s):  
François Marillier ◽  
Charlotte E. Keen ◽  
Glen S. Stockmal ◽  
Garry Quinlan ◽  
Harold Williams ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Surface Expression ◽  
Seismic Profiles ◽  
Crust And Upper Mantle ◽  
Seismic Reflection Data ◽  
Central Block ◽  
Reflection Data ◽  
Lower Crustal ◽  
Canadian Appalachians

In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.

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