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Publication
Signature of fault zone deformation in near-surface soil visible in shear wave seismic reflections
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Advisor(s)
Abstract(s)
Small-throw seismogenic fault segments hidden in the Holocene sediments are crucial but difficult targets in seismic exploration. We report here the detection
of the deformation pattern and a concealed fault segment in the unconsolidated sediments at Vila Franca Xira, Portugal, through identification in shear wave
reflection data of multiple signatures of ductile deformation associated with faulting. We find step-like changes in the stacking velocity along a shallow
subsoil layer boundary, indicating synsedimentary faulting. We also recognize a consistent distortion in the moveout of the reflection events in the raw shear
wave data. Synthetic modeling of seismic data helps in interpreting these observations and identifying backscattered energy from a steeply dipping shallow
fault zone. Prior to this finding, there was no evidence for Holocene activity of this fault, although the fault is considered to be the most probable source for
the disastrous 1531 earthquake.
Description
Keywords
Prospecção sísmica Falhas Deformação Ondas sísmicas Reflexão sísmica Falha de Vila Franca de Xira (Portugal)
Citation
Ghose, Ranajit; Carvalho, João; Loureiro, Afonso - Signature of fault zone deformation in near-surface soil visible in shear wave seismic reflections. In: Geophysical Research Letters, Vol. 40, Issue 6 (28 March 2013), p. 1074-1078