Paleoseismology investigates geologic structures and sediments for the evidence of ancient seismic events. Shallow Quaternary sediments are commonly studied using several geologic and geophysical techniques. Ground penetrating radar (GPR) uses high-frequency electromagnetic impulses to probe the underground, resulting in an high resolution imaging of the shallow subsurface. The acquisition of GPR data over a dense enough grid, allow to study geologic structures in their actual three dimensional geometric setting. We are presenting a GPR survey made across the Mt. Vettore fault, in the Central Apennines (Italy), in order to enrich informations on this silent fault obtained previously by direct paleoseismologic analysis made by trenching the fault zone. We first localized the fault with some reconnaissance profiles across a small scarp over a Late PleistoceneHolocene alluvial fan, then we estimated the dielectric properties of the medium with two velocity profiles. After the preliminary measurements, we acquired radar data over a 20x20 m survey grid opportunely spaced to avoid signal aliasing. After processing, this data furnishes a detailed three dimensional image of the SSENNO fault, so that the both the geometric and compositional features can be studied. We detected the main trend of the fault and also two main radar facies have been identified, corresponding to the sedimentary units at the hangingwall and footwall of the main fault strand. GPR showed itself to be an effective method to extend bi-dimensional data to a three dimensional environment. In particular in this work, direct trench observation from previous studies and radar data showed their mutual usefulness, and this confirm the Ground Penetrating Radar to be a particularly useful tool for the paleoseismologic studies.
3D GPR investigation along Mt. Vettore Fault (Pian Grande/Castelluccio di Norcia-Umbria
ERCOLI, MAURIZIO;FRIGERI, ALESSANDRO;PAUSELLI, Cristina;FEDERICO, Costanzo
2009
Abstract
Paleoseismology investigates geologic structures and sediments for the evidence of ancient seismic events. Shallow Quaternary sediments are commonly studied using several geologic and geophysical techniques. Ground penetrating radar (GPR) uses high-frequency electromagnetic impulses to probe the underground, resulting in an high resolution imaging of the shallow subsurface. The acquisition of GPR data over a dense enough grid, allow to study geologic structures in their actual three dimensional geometric setting. We are presenting a GPR survey made across the Mt. Vettore fault, in the Central Apennines (Italy), in order to enrich informations on this silent fault obtained previously by direct paleoseismologic analysis made by trenching the fault zone. We first localized the fault with some reconnaissance profiles across a small scarp over a Late PleistoceneHolocene alluvial fan, then we estimated the dielectric properties of the medium with two velocity profiles. After the preliminary measurements, we acquired radar data over a 20x20 m survey grid opportunely spaced to avoid signal aliasing. After processing, this data furnishes a detailed three dimensional image of the SSENNO fault, so that the both the geometric and compositional features can be studied. We detected the main trend of the fault and also two main radar facies have been identified, corresponding to the sedimentary units at the hangingwall and footwall of the main fault strand. GPR showed itself to be an effective method to extend bi-dimensional data to a three dimensional environment. In particular in this work, direct trench observation from previous studies and radar data showed their mutual usefulness, and this confirm the Ground Penetrating Radar to be a particularly useful tool for the paleoseismologic studies.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
