TY - JOUR
T1 - Characterization of an intraplate seismogenic zone using geophysical and borehole data
T2 - The vila Franca de Xira Fault, Portugal
AU - Carvalho, João
AU - Alves, Daniela
AU - Cabral, João
AU - Ghose, Ranajit
AU - Borges, José
AU - Dias, Ruben
AU - Ramalho, Elsa
AU - Caldeira, Bento
AU - Casacão, João
AU - Leote, Jaime
PY - 2020
Y1 - 2020
N2 - The Vila Franca de Xira (VFX) fault is a regional fault zone located about 25 km northeast of Lisbon, affecting Neogene sediments. Recent shear-wave seismic studies show that this complex fault zone is buried beneath Holocene sediments and is deforming the alluvial cover, in agreement with a previous work that proposes the fault as the source of the 1531 Lower Tagus Valley earthquake. In this work, we corroborate these results using S-wave, P-wave, geoelectric, ground-penetrating radar and borehole data, confirming that the sediments deformed by several fault branches are of Upper Pleistocene to Holocene. Accumulated fault vertical offsets of about 3 m are estimated from the integrated interpretation of geophysical and borehole data, including 2D elastic seismic modeling, with an estimated resolution of about 0.5 m. The deformations affecting the Tagus alluvial sediments probably resulted from surface or near-surface rupture of the VFX fault during M∼7 earthquakes, reinforcing the fault as the seismogenic source of regional historical events, as in 1531, and highlighting the need for preparedness for the next event.
AB - The Vila Franca de Xira (VFX) fault is a regional fault zone located about 25 km northeast of Lisbon, affecting Neogene sediments. Recent shear-wave seismic studies show that this complex fault zone is buried beneath Holocene sediments and is deforming the alluvial cover, in agreement with a previous work that proposes the fault as the source of the 1531 Lower Tagus Valley earthquake. In this work, we corroborate these results using S-wave, P-wave, geoelectric, ground-penetrating radar and borehole data, confirming that the sediments deformed by several fault branches are of Upper Pleistocene to Holocene. Accumulated fault vertical offsets of about 3 m are estimated from the integrated interpretation of geophysical and borehole data, including 2D elastic seismic modeling, with an estimated resolution of about 0.5 m. The deformations affecting the Tagus alluvial sediments probably resulted from surface or near-surface rupture of the VFX fault during M∼7 earthquakes, reinforcing the fault as the seismogenic source of regional historical events, as in 1531, and highlighting the need for preparedness for the next event.
UR - http://www.scopus.com/inward/record.url?scp=85089627716&partnerID=8YFLogxK
U2 - 10.1785/0220190317
DO - 10.1785/0220190317
M3 - Article
AN - SCOPUS:85089627716
SN - 0895-0695
VL - 91
SP - 2287
EP - 2297
JO - Seismological Research Letters
JF - Seismological Research Letters
IS - 4
ER -