Shallow Seismic Velocity Structure of the Betic Cordillera (Southern Spain) from Modelling of Rayleigh Wave Dispersion |
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| Authors: | M?Chourak Email author" target="_blank">V?CorcheteEmail author J?Badal F?Gómez J?Serón |
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| Institution: | 1.Applied Physics, Higher Polytechnic School,University of Almería,Ca?ada de San Urbano,Spain;2.Physics of the Earth, Sciences B,University of Zaragoza,Zaragoza,Spain;3.Computation Sciences, Higher Polytechnic Center,University of Zaragoza,Maria de Luna 3,Zaragoza,Spain |
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| Abstract: | A detailed dispersion analysis of Rayleigh waves generated by local earthquakes and occasionally by blasts that occurred in
southern Spain, was undertaken to obtain the shear-wave velocity structure of the region at shallow depth. Our database includes
seismograms generated by 35 seismic events that were recorded by 15 single-component short-period stations from 1990 to 1995.
All these events have focal depths less than 10 km and body-wave magnitudes between 3.0 and 4.0, and they were all recorded
at distances between 40 and 300 km from the epicentre. We analysed a total of 90 source-station Rayleigh-wave paths. The collected
data were processed by standard digital filtering techniques to obtain Rayleigh-wave group-velocity dispersion measurements.
The path-averaged group velocities vary from 1.12 to 2.25 km/s within the 1.0-6.0 s period interval. Then, using a stochastic
inversion approach we obtained 1-D shear-wave velocity–depth models across the study area, which were resolved to a depth
of circa 5 km. The inverted shear-wave velocities range approximately between 1.0 and 3.8 km/s with a standard deviation range
of 0.05–0.16 km/s, and show significant variations from region to region. These results were combined to produce 3-D images
via volumetric modelling and data visualization. We present images that show different shear velocity patterns for the Betic
Cordillera. Looking at the velocity distribution at various depths and at vertical sections, we discuss of the study area
in terms of subsurface structure and S-wave velocity distribution (low velocity channels, basement depth, etc.) at very shallow
depths (0–5 km). Our results characterize the region sufficiently and lead to a correlation of shear-wave velocity with the
different geological units features. |
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| Keywords: | 3-D images Betic Cordillera dispersion inversion Rayleigh waves seismic velocity structure |
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