scholarly journals Can a narrow, melt-rich, low-velocity zone of mantle upwelling be hidden beneath the East Pacific Rise? Limits from waveform modeling and the MELT Experiment

2000 ◽  
Vol 105 (B4) ◽  
pp. 7945-7960 ◽  
Author(s):  
Shu-Huei Hung ◽  
Donald W. Forsyth ◽  
Douglas R. Toomey
Keyword(s):  
East Pacific Rise ◽  
Mantle Upwelling ◽  
Low Velocity ◽  
Waveform Modeling ◽  
Low Velocity Zone ◽  
East Pacific ◽  
Velocity Zone

Seismic attenuation near the East Pacific Rise and the origin of the low-velocity zone

2007 ◽  
Vol 258 (1-2) ◽  
pp. 260-268 ◽  
Author(s):  
Yingjie Yang ◽  
Donald W. Forsyth ◽  
Dayanthie S. Weeraratne
Keyword(s):  
East Pacific Rise ◽  
Seismic Attenuation ◽  
Low Velocity ◽  
Low Velocity Zone ◽  
East Pacific ◽  
Velocity Zone

scholarly journals Long-period P waveform modeling of upper mantle phases in the West Mediterranean basin

1994 ◽  
Vol 37 (1) ◽  
Author(s):  
N. A. Pino
Keyword(s):  
Upper Mantle ◽  
Velocity Model ◽  
Low Velocity ◽  
Waveform Modeling ◽  
Low Velocity Zone ◽  
Velocity Models ◽  
Long Period ◽  
Crustal Earthquakes ◽  
Lower Amplitude ◽  
Velocity Zone

Long-period P waveforms of some Italian crustal earthquakes recorded at the WWSSN stations located in the Iberian Peninsula have been modeled to derive a 1D upper matle compressional velocity model. A technique based on the Cagniard-de Hoop method has been used to compute synthetic seismograms. Waveforms have first been computed for published velocity models referred to different tectonic provinces and compared with the data. A model that strongly improves the fits to the data is then presented. The proposed model, called WMP, is characterized by a 100 km thick lid overlaying a low velocity zone, a 1% velocity discontinuity located at 313 km depth, that is required to fit a lower amplitude phase, and an abrupt increase in the velocity gradient starting from 370 km. This latter is preferred to the sharp discontinuity located at about 400 km that is present in various models obtained for upper mantle structure with analogous techniques. Within the lid and the low-velocity zone, WMP displays features that are typical of old ocean structures like the Northwest Atlantic Ocean.

Partial melting and the low-velocity zone

1970 ◽  
Vol 4 (1) ◽  
pp. 62-64 ◽  
Author(s):  
Don L. Anderson ◽  
Hartmut Spetzler
Keyword(s):  
Partial Melting ◽  
Low Velocity ◽  
Low Velocity Zone ◽  
Velocity Zone

Nature of the low velocity zone in Cascadia from receiver function waveform inversion

2012 ◽  
Vol 337-338 ◽  
pp. 25-38 ◽  
Author(s):  
Ralf T.J. Hansen ◽  
Michael G. Bostock ◽  
Nikolas I. Christensen
Keyword(s):  
Receiver Function ◽  
Waveform Inversion ◽  
Low Velocity ◽  
Low Velocity Zone ◽  
Velocity Zone

scholarly journals Fault Zone Guided Wave generation on the locked, late interseismic Alpine Fault, New Zealand

2021 ◽  
Author(s):  
JD Eccles ◽  
AK Gulley ◽  
PE Malin ◽  
CM Boese ◽  
John Townend ◽  
...  
Keyword(s):  
Fault Zone ◽  
Plate Boundary ◽  
Guided Wave ◽  
S Wave ◽  
Low Velocity ◽  
Catchment Scale ◽  
Near Surface ◽  
Low Velocity Zone ◽  
Alpine Fault ◽  
Velocity Zone

© 2015. American Geophysical Union. All Rights Reserved. Fault Zone Guided Waves (FZGWs) have been observed for the first time within New Zealand's transpressional continental plate boundary, the Alpine Fault, which is late in its typical seismic cycle. Ongoing study of these phases provides the opportunity to monitor interseismic conditions in the fault zone. Distinctive dispersive seismic codas (~7-35Hz) have been recorded on shallow borehole seismometers installed within 20m of the principal slip zone. Near the central Alpine Fault, known for low background seismicity, FZGW-generating microseismic events are located beyond the catchment-scale partitioning of the fault indicating lateral connectivity of the low-velocity zone immediately below the near-surface segmentation. Initial modeling of the low-velocity zone indicates a waveguide width of 60-200m with a 10-40% reduction in S wave velocity, similar to that inferred for the fault core of other mature plate boundary faults such as the San Andreas and North Anatolian Faults.

Topology of ray surfaces in low-velocity zones

1979 ◽  
Vol 69 (2) ◽  
pp. 369-378
Author(s):  
George A. McMechan
Keyword(s):  
Guided Waves ◽  
Turning Points ◽  
Three Dimensional ◽  
Focal Depth ◽  
Low Velocity ◽  
Low Velocity Zone ◽  
Ray Trajectories ◽  
Definition Of ◽  
Single Set ◽  
Velocity Zone

abstract Plotting of three-dimensional ray surfaces in p-Δ-z space provides a means of determining p-Δ curves for any focal depth. A region of increasing velocity with depth is represented in p-Δ-z space by a trough, and a region of decreasing velocity, by a crest. Two sets of ray trajectories, the arrivals refracted outside a low-velocity zone, and the guided waves inside the zone, can be merged into a single set along the ray that splits into two at the top of the low-velocity zone. This ray is common to both sets. This construction provides continuity of the locus of ray turning points through the low-velocity zone and thus allows definition of p-Δ curves inside as well as outside the low-velocity zone.

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