scholarly journals Lateral variations of shallow shear-velocity structure in southwestern Taiwan inferred from short-period Rayleigh waves

2003 ◽  
Vol 55 (6) ◽  
pp. 349-354 ◽  
Author(s):  
Ruey-Der Hwang ◽  
Guey-Kuen Yu ◽  
Wen-Yen Chang ◽  
Jo-Pan Chang
Keyword(s):  
Rayleigh Waves ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Short Period ◽  
Southwestern Taiwan ◽  
Lateral Variations

Rayleigh waves in southern New Guinea

1969 ◽  
Vol 59 (2) ◽  
pp. 945-958 ◽  
Author(s):  
J. A. Brooks
Keyword(s):  
Rayleigh Waves ◽  
Velocity Structure ◽  
Group Velocity Dispersion ◽  
Focal Depth ◽  
New Guinea ◽  
Shear Velocity ◽  
Stationary Wave ◽  
Period Range ◽  
Mode Group ◽  
Path Lengths

abstract A shear velocity structure having features similar to the Gutenberg model for the upper 200 km of the mantle is consistent with features of higher mode Rayleighwave group-velocity dispersion curves in the period range 4 to 30 seconds, for paths across southern New Guinea. Pronounced discontinuities appear to be absent within the crust where shear velocities are expected to gradually increase with depth. Clearly dispersive second mode (M21) Rayleigh waves, well separated in time from the fundamental mode, are shown for path lengths less than 2000 km. Frequencies excited show some dependence on focal depth. Stationary wave groups of period 10-20 seconds, very like the Sa phase, and generated by earthquakes of focal depth between 100 and 160 km coincide with expected normal mode group arrivals.

Reflection, refraction and mode conversion of long-period surface waves and the measurement of Q−1 for free oscillations

1973 ◽  
Vol 63 (5) ◽  
pp. 1709-1722
Author(s):  
Leon Reiter
Keyword(s):  
Surface Waves ◽  
Fundamental Mode ◽  
Rayleigh Waves ◽  
Velocity Structure ◽  
Fourier Transforms ◽  
Mode Conversion ◽  
Power Spectra ◽  
Peak Frequency ◽  
Earth Structure ◽  
Lateral Variations

abstract Filtered time series of Rayleigh waves from 4 events recorded on the quartz accelerometer at the IGPP, Camp Elliott Station, were analyzed. Attenuation (Q−1) was computed for spheroidal fundamental modes (oS19 to oS24) from several sequences of time-lapsed records for each event. A five-fold variation in measured Q−1 (and some variations in peak frequency) was assumed to be the result of lateral inhomogeneities in earth structure. Utilizing the duality between Rayleigh waves and fundamental-mode spheroidal oscillations, model power spectra were computed by summing the simulated Fourier transforms of dispersed wave trains. The effect of lateral variations in earth structure resulting in reflection, refraction and mode conversion of fundamental-mode surface waves was simulated by changes in amplitude, phase angle, and group and component travel times. Assuming an anelastic 10,000/Q of 33.3 (Q = 300), the observed range of measured Q−1 (and peak frequency) variations was duplicated by models with up to 5 per cent of the fundamental-mode Rayleigh-wave energy being “scattered”, i.e., reflected, refracted or converted to higher modes. In the real Earth, this would call for lateral variations in velocity structure well below the upper few hundred kilometers of the mantle. Recent seismological investigations have suggested lateral variations at these depths.

scholarly journals Shear velocity structure in the Aegean area obtained by inversion of Rayleigh waves

2004 ◽  
Vol 160 (1) ◽  
pp. 127-143 ◽  
Author(s):  
E. E. Karagianni ◽  
C. B. Papazachos ◽  
D. G. Panagiotopoulos ◽  
P. Suhadolc ◽  
A. Vuan ◽  
...  
Keyword(s):  
Rayleigh Waves ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Aegean Area

Dispersion of Short Period Rayleigh Waves Within The Ozark Uplift and Illinois Basin

1989 ◽  
Vol 60 (3) ◽  
pp. 111-118 ◽  
Author(s):  
Mark T. Woods ◽  
David R. Russell ◽  
Robert B. Herrmann
Keyword(s):  
Velocity Structure ◽  
Group Velocity Dispersion ◽  
Regional Scale ◽  
Single Layer ◽  
Shear Velocity ◽  
Scale Model ◽  
Illinois Basin ◽  
Short Period ◽  
New Models ◽  
Different Parts

Abstract We use data recorded by four arrays of portable instruments to investigate the propagation of short period (0.2≤T ≤2.0 sec) surface waves within the Ozark Uplift and Illinois Basin. At the regional scale, we construct group velocity dispersion curves for five suites of propagation paths, and invert them for shear velocity structure. The best model in each case consists of a single layer above a halfspace, and we can correlate the model units with geologic formations. The upper layer in the two Ozark Uplift models represents Ordovician and Cambrian carbonate strata, the halfspace corresponds to the Precambrian crystalline basement. Differences between our new models and an earlier one reflect the different parts of uplift that were sampled, and show the thickening of the Paleozoic section away from the uplift core. In the Illinois Basin models, the upper layer represents Pennsylvanian age elastics and the halfspace represents older Paleozoic carbonates. This interpretation is substantiated by a velocity log from a nearby deep well. Again, differences between our new models and earlier efforts result from different passband data that sample different parts of the basin. We also extract interstation phase velocities from array data recorded at the western edge of the Illinois Basin, over Mississippian age outcrop. By comparing this local dispersion curve with one calculated from the appropriate regional scale model, we conclude that the local structure can also be modeled as a single layer above a halfspace. Local shear velocities are, however, 30% faster than the regional average, which reflects the absence of the slow Pennsylvanian elastic strata around the basin’s periphery.

Sign in / Sign up

Export Citation Format

Share Document