scholarly journals Complex structure of the lithospheric slab beneath the Banda arc, eastern Indonesia depicted by a seismic tomographic model

2011 ◽  
Vol 1 (1) ◽  
pp. 1 ◽  
Author(s):  
Sri Widiyantoro ◽  
Jeremy D. Pesicek ◽  
Clifford H. Thurber
Keyword(s):  
Upper Mantle ◽  
Velocity Structure ◽  
Complex Structure ◽  
P Wave ◽  
Zone Structure ◽  
Study Region ◽  
Tomographic Images ◽  
P Wave Velocity ◽  
Banda Arc ◽  
Back Arc

Seismic tomography with a non-linear approach has been successfully applied to image the P-wave velocity structure beneath the Banda arc in detail. Nearly one million compressional phases including the surfacereflected depth phases pP and pwP from events within the Indonesian region have been used. The depth phases have been incorporated in order to improve the sampling of the uppermantle structure, particularly below the Banda Sea in the back-arc regions. For the model parameterization, we have combined a highresolution regional inversion with a low-resolution global inversion to allow detailed images of slab structures within the study region and to minimize the mapping of distant aspherical mantle structure into the volume under study. In this paper, we focus our discussion on the upper mantle and transition zone structure beneath the curved Banda arc. The tomographic images confirm previous observations of the twisting of the slab in the upper mantle, forming a spoon-shaped structure beneath the Banda arc. A slab lying flat on the 660 km discontinuity beneath the Banda Sea is also well imaged. Further interpretations of the resulting tomograms and seismicity data support the scenario of the Banda arc subduction rollback.

Upper mantle P-wave velocity structure in the Japan region from travel-time studies of deep earthquakes using a new analytical method

1971 ◽  
Vol 61 (6) ◽  
pp. 1549-1570
Author(s):  
K. L. Kaila ◽  
V. G. Krishna ◽  
Hari Narain
Keyword(s):  
Wave Velocity ◽  
Calibration Curve ◽  
Velocity Gradient ◽  
Upper Mantle ◽  
Inflection Point ◽  
Velocity Structure ◽  
P Wave ◽  
Central Japan ◽  
P Wave Velocity ◽  
P Wave Velocity Structure

abstract The upper mantle P-wave velocity structure of the region of Japan has been studied in great detail from travel times of 107 earthquakes with focal depths varying from 40 to 600 km, using a new analytical method given by Kaila (1969). In southwestern Japan the P-wave velocity is found to be 7.88 km/sec at a 40-km depth, and it remains almost constant to a depth of 255 km. For northeastern Japan the velocity, determined as 7.88 km/sec at 40 km, increases linearly with moderate gradient to 8.14 km/sec at a 175-km depth. On the other hand, for central Japan the P-velocity is found to be 7.92 km/sec at a 40-km depth, and increases linearly with a high-velocity gradient to 8.33 km/sec at a depth of 180 km. Then, there is a slight decrease in the velocity gradient, but the velocity still increases linearly to 8.52 km/sec at a depth of 365 km. At this transition depth, there is a first-order velocity discontinuity—the velocity increasing from 8.52 to 9.10 km/sec. Below this depth, velocity again increases linearly from 9.10 to 9.99 km/sec at a depth of 600 km. Probable causes for these lateral-velocity inhomogeneities in the upper mantle of the Japan region are discussed. Graphs have been drawn to show the variation with depth of Δ*, the epicentral distance to the inflection point, (Δ2 − Δ1), ptrue = ∂T/∂Δ and ap = (T − pΔ) at the inflection point, the latter acting as a calibration curve for earthquake focal-depth determination in Japan. Using this calibration curve, focal depths are redetermined for all of the earthquakes under study for central Japan, and the same are compared with the values reported in the International Seismological Summaries.

P-Wave Residuals in Western Canada

1975 ◽  
Vol 12 (2) ◽  
pp. 174-181
Author(s):  
E. J. Roebroek ◽  
E. Nyland
Keyword(s):  
United States ◽  
Wave Velocity ◽  
Upper Mantle ◽  
Velocity Structure ◽  
The United States ◽  
P Wave ◽  
Western Canada ◽  
Lateral Variation ◽  
P Wave Velocity ◽  
P Wave Velocity Structure

A study of over 1500 P-wave phases which pass, for the most part, through the upper mantle beneath Western Canada, shows that there is no significant lateral variation in P-wave velocity structure beneath Western Canada, and that the Wiggins and Helmberger model for the Western regions of the United States does not fit the data for Western Canada.One possible interpretation of the data for Western Canada is closer to the classical Herrin model of P-wave velocity as a function of depth than it is to the Wiggins and Helmberger A model.

scholarly journals Upper mantle P wave velocity structure and transition zone thickness beneath the Arabian Shield

2003 ◽  
Vol 30 (10) ◽  
pp. n/a-n/a ◽  
Author(s):  
Margaret H. Benoit ◽  
Andrew A. Nyblade ◽  
John C. VanDecar ◽  
Harold Gurrola
Keyword(s):  
Transition Zone ◽  
Wave Velocity ◽  
Upper Mantle ◽  
Velocity Structure ◽  
P Wave ◽  
Arabian Shield ◽  
P Wave Velocity ◽  
P Wave Velocity Structure

UPPER MANTLE STRUCTURE IN CANADA FROM SEISMIC OBSERVATIONS USING CHEMICAL EXPLOSIONS

1967 ◽  
Vol 4 (5) ◽  
pp. 961-975 ◽  
Author(s):  
K. G. Barr
Keyword(s):  
Wave Velocity ◽  
Upper Mantle ◽  
Velocity Structure ◽  
P Wave ◽  
Hudson Bay ◽  
S Wave ◽  
Low Velocity ◽  
P Wave Velocity ◽  
Upper Mantle Structure ◽  
Chemical Explosions

Long-range seismic observations at the standard Canadian seismic stations, from chemical explosions in Hudson Bay and Lake Superior, are used to derive a P-wave velocity structure for the upper mantle. The coordinates of observed cusps are used to define the structural discontinuities. These discontinuities are at depths of 126 and 366 km, which agree closely with the depths of the S-wave velocity discontinuities deduced from surface-wave observations. The observations do not require a low velocity layer in the upper mantle.

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