Seismic Structure of the Crust and Uppermost Mantle of North America and Adjacent Oceanic Basins: A Synthesis

2002 ◽  
Vol 92 (6) ◽  
pp. 2478-2492 ◽  
Author(s):  
G. S. Chulick
Keyword(s):  
North America ◽  
Seismic Structure ◽  
Uppermost Mantle

scholarly journals Seismic structure of the crust and uppermost mantle in the incipient stage of back arc rifting - northernmost Okinawa Trough

2004 ◽  
Vol 31 (2) ◽  
Author(s):  
Kazuo Nakahigashi ◽  
Masanao Shinohara ◽  
Sadaomi Suzuki ◽  
Ryota Hino ◽  
Hajime Shiobara ◽  
...  
Keyword(s):  
Okinawa Trough ◽  
Seismic Structure ◽  
Uppermost Mantle ◽  
Incipient Stage ◽  
Back Arc

Seismic structure of the uppermost mantle beneath the Kenya rift

1994 ◽  
Vol 236 (1-4) ◽  
pp. 201-216 ◽  
Author(s):  
G.R. Keller ◽  
James Mechie ◽  
L.W. Braile ◽  
W.D. Mooney ◽  
Claus Prodehl
Keyword(s):  
Seismic Structure ◽  
Uppermost Mantle ◽  
Kenya Rift

Crustal seismic structure beneath the Garhwal Himalaya using regional and teleseismic waveform modelling

2020 ◽  
Vol 222 (3) ◽  
pp. 2040-2052
Author(s):  
Nagaraju Kanna ◽  
Sandeep Gupta
Keyword(s):  
Receiver Function ◽  
Garhwal Himalaya ◽  
Moho Depth ◽  
Seismic Structure ◽  
Uppermost Mantle ◽  
Seismic Stations ◽  
Wave Velocities ◽  
Function Modelling ◽  
Partial Melts ◽  
Lower Crustal

SUMMARY We investigate the crustal seismic structure of the Garhwal Himalayan region using regional and teleseismic earthquake waveforms, recorded over 19 closely spaced broad-band seismic stations along a linear profile that traverses from the Sub Himalayas to Higher Himalayas. The regional earthquake traveltime analysis provides uppermost mantle P- and S-wave velocities as 8.2 and 4.5 km s−1, respectively. The calculated receiver functions from the teleseismic P waveforms show apparent P-to-S conversions from the Moho as well as from intracrustal depths, at most of the seismic stations. These conversions also show significant azimuthal variations across the Himalayas, indicating complex crustal structure across the Garhwal Himalaya. We constrain the receiver function modelling using the calculated uppermost mantle (Pn and Sn) velocities. Common conversion point stacking image of P-to-S conversions as well as receiver function modelling results show a prominent intracrustal low shear velocity layer with a flat–ramp–flat geometry beneath the Main Central Thrust zone. This low velocity indicates the possible presence of partial melts/fluids in the intracrustal depths beneath the Garhwal Himalaya. We correlate the inferred intracrustal partial melts/fluids with the local seismicity and suggest that the intracrustal fluids are one of the possible reasons for the occurrence of upper-to-mid-crustal earthquakes in this area. The results further show that the Moho depth varies from ∼45 km beneath the Sub Himalayas to ∼58 km to the south of the Tethys Himalayas. The calculated lower crustal shear wave velocities of ∼3.9 and 4.3 km s−1 beneath the Lesser and Higher Himalayas suggest the presence of granulite and partially eclogite rocks in the lower crust below the Lesser and Higher Himalayas, respectively. We also suggest that the inferred lower crustal rocks are the possible reasons for the presence and absence of the lower crustal seismicity beneath the Lesser and Higher Himalayas, respectively.

Seismic structure of the crust and uppermost mantle beneath Caucasus based on regional earthquake tomography

2016 ◽  
Vol 119 ◽  
pp. 87-99 ◽  
Author(s):  
Irina Zabelina ◽  
Ivan Koulakov ◽  
Iason Amanatashvili ◽  
Sami El Khrepy ◽  
Nassir Al-Arifi
Keyword(s):  
Seismic Structure ◽  
Uppermost Mantle ◽  
Regional Earthquake

scholarly journals Regional site response and uppermost mantle seismic structure of central and eastern united states

2019 ◽  
Author(s):  
◽  
Rayan Yassminh
Keyword(s):  
United States ◽  
New England ◽  
Velocity Ratio ◽  
Site Amplification ◽  
P Wave ◽  
Seismic Structure ◽  
Eastern United States ◽  
Uppermost Mantle ◽  
Pn Velocity ◽  
Mantle Temperature

This dissertation examines seismological data from regional earthquake sources in order to examine the seismological character of the crust and uppermost mantle in central and eastern United States. Firstly, site amplification of regional highfrequency Lg seismic phases is estimate ed using a Reverse-Two Station (RTS) method. RTS results show topography and sediment thickness are likely to affect amplification and both factors likely frequency-dependent. There is a negative correlation between the RTS-measured amplification and shallow shear-wave velocity. It appears that both regional topography (i.e., long-wavelength topography) and deeper subsurface seismic structures (basins and sediments) have a large impact on site amplification. Subsequently, Pn and Sn travel time tomography is used to estimate the upper most mantle P-wave (Pn) velocity, S-wave (Sn) velocity, and the velocity ratio (VPn/VSn). In addition to velocity, effective attenuation of Sn phase (Q[superscript -1]sn) is also measured. The result shows regions of high velocity such as southern Georgia, eastern South Carolina and NMSZ and low Q[subscript Sn] values. The V[subscript Pn]/V[subscript Sn] ratio shows values higher than the average in regions such as the Mississippi Embayment, New England, and south Appalachian. V[subscript Pn]/V[subscript Sn] ratios are lower than the average in regions such as northwestern CEUS, South Georgia and eastern Texas. We estimated the uppermost mantle temperature by applying a constrained grid-search algorithm includes the observed V[subscript Sn], V[subscript Pn] and Q[subscript Sn] with the calculated velocities of specific compositional models. The uppermost mantle temperature result, [about]300-500C, beneath the northern mid-continent, and the highest temperature, 1100 C, beneath New England

Seismic structure of the crust and uppermost mantle of the Capricorn and Paterson Orogens and adjacent cratons, Western Australia, from passive seismic transects

2012 ◽  
Vol 196-197 ◽  
pp. 295-308 ◽  
Author(s):  
Anya M. Reading ◽  
Hrvoje Tkalčić ◽  
Brian L.N. Kennett ◽  
Simon P. Johnson ◽  
Stephen Sheppard
Keyword(s):  
Western Australia ◽  
Seismic Structure ◽  
Uppermost Mantle ◽  
Passive Seismic
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