Premium
Calibrating 3D tomograms of a granitic pluton
Author(s) -
Martí D.,
Carbonell R.,
Tryggvason A.,
Escuder J.,
PérezEstaún A.
Publication year - 2002
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2001gl012942
Subject(s) - geology , borehole , seismology , tomography , pluton , fracture (geology) , p wave , seismic tomography , azimuth , mineralogy , petrology , geophysics , geometry , geotechnical engineering , mantle (geology) , optics , tectonics , medicine , physics , mathematics , cardiology , atrial fibrillation
First arrival‐time P‐waves from offset and azimuth variable vertical seismic reflection records are used to tomographically reconstruct the 3D P‐wave velocity structure around a 500 m deep vertical borehole. Comparisons with sonic and fracture index logs and core samples indicates that low velocity anomalies in the tomograms correlate with surface mapped fracture zones. Results also show that low velocity zones intersect the borehole in areas characterized by relatively low values for Vp and Vs determined from sonic logs. These zones are characterized by Poisson's ratio (σ) close to 0.3, which are indicative of altered or fractured rock and supported by the fracture index and core samples. The high velocity anomalies intersect the well in areas characterized by low values of the fracture index and σ = 0.25 or lower. This suggests that the relatively high Vp velocities are indicative of unfractured rock. This study reveals that high resolution tomography produces results consistent with direct observations in a well‐sampled borehole.