GULF COAST SURFACE WAVES

Geophysics ◽  
1953 ◽  
Vol 18 (1) ◽  
pp. 41-53 ◽  
Author(s):  
Lynn G. Howell ◽  
E. F. Neuenschwander ◽  
A. L. Pierson
Keyword(s):  
Rayleigh Wave ◽  
Surface Waves ◽  
Velocity Dispersion ◽  
Gulf Coast ◽  
Group Velocity Dispersion ◽  
Vertical Strain ◽  
Long Period ◽  
Short Period ◽  
Component Velocity ◽  
Wave Trains

Surface wave recordings were made with the following: a three‐component velocity seismometer, a long‐period displacement seismometer, six dynamic seismometers, an air‐actuated condenser microphone, and a vertical strain seismometer. Wave trains were recorded similar to those obtained by B. F. Howell in California. We have divided the surface waves into two trains instead of three. The early train seems to have properties of the M‐2 wave of Sezawa; the late train seems to be a Rayleigh wave. An air‐coupled wave is shown to be associated with the M‐2 wave. In the group velocity dispersion curve of the Rayleigh wave, the short‐period branch was found as predicted by theory as well as the usually observed long‐period branch. By making certain assumptions, the thickness of the top layer appears to be about 50 feet according to the theoretical curves of Kanai.

Extracting Long-Period Surface Waves and Free Oscillations Using Ambient Noise Recorded by Global Distributed Superconducting Gravimeters

2020 ◽  
Vol 91 (4) ◽  
pp. 2234-2246
Author(s):  
Hang Li ◽  
Jianqiao Xu ◽  
Xiaodong Chen ◽  
Heping Sun ◽  
Miaomiao Zhang ◽  
...  
Keyword(s):  
Surface Waves ◽  
Group Velocity ◽  
Ambient Noise ◽  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
Dispersion Curves ◽  
Free Oscillations ◽  
Long Period ◽  
Superconducting Gravimeters ◽  
Noise Data

Abstract Inversion of internal structure of the Earth using surface waves and free oscillations is a hot topic in seismological research nowadays. With the ambient noise data on seismically quiet days sourced from the gravity tidal observations of seven global distributed superconducting gravimeters (SGs) and the seismic observations for validation from three collocated STS-1 seismometers, long-period surface waves and background free oscillations are successfully extracted by the phase autocorrelation (PAC) method, respectively. Group-velocity dispersion curves at the frequency band of 2–7.5 mHz are extracted and compared with the theoretical values calculated with the preliminary reference Earth model. The comparison shows that the best observed values differ about ±2% from the corresponding theoretical results, and the extracted group velocities of the best SG are consistent with the result of the collocated STS-1 seismometer. The results indicate that reliable group-velocity dispersion curves can be measured with the ambient noise data from SGs. Furthermore, the fundamental frequency spherical free oscillations of 2–7 mHz are also clearly extracted using the same ambient noise data. The results in this study show that the SG, besides the seismometer, is proved to be another kind of instrument that can be used to observe long-period surface waves and free oscillations on seismically quiet days with a high degree of precision using the PAC method. It is worth mentioning that the PAC method is first and successfully introduced to analyze SG observations in our study.

Worldwide investigation of the mantle Rayleigh-wave group velocities

1973 ◽  
Vol 63 (1) ◽  
pp. 271-281
Author(s):  
Harsh K. Gupta ◽  
Tetsuo Santô
Keyword(s):  
Rayleigh Wave ◽  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
Great Circle ◽  
Wave Group ◽  
High Group ◽  
Period Range ◽  
Very High ◽  
Group Velocities ◽  
Existing Data

abstract An attempt to apply the crossing path technique to the division of the globe into similar regions of mantle Rayleigh-wave group-velocity dispersion characteristics failed because of the paucity of existing data (for about 80 great-circle paths). As a first step to achieve this goal, mantle Rayleigh-wave group velocities have been obtained for 31 new great-circle paths in the 80- to 240-sec period range. The data have been divided into four groups on the basis of dispersion behavior and compared with Dziewonski's (1971) results. An interesting finding has been the very high group velocities for the 6-MUN path, higher than any reported so far.

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