The September 26, 1997 Colfiorito, Italy, earthquakes: Modeled coseismic surface displacement from SAR interferometry and GPS

Abstract

Abstract.The largest events of the 1997 UmbriaMarche seismic sequence were the two September 26 earthquakes of Mw=5.7 (00:33 GMT) and Mw=6.0 (09:40 GMT), which caused severe damage and ground cracks in a wide area around the epicenters. We created an ERS-SAR differential interferogram, where nine fringes are visible in and around the Colfiorito basin, corresponding to 25 cm of coseismic surface displacement. GPS data show a maximum horizontal displacement of (14 + 1.8) cm and a maximum subsidence of (24 + 3) cm. We used these geodetic data and the seismological parameters to estimate geometry and slip distribution on the fault planes. Modeled fault depths and maximum slip amplitudes are 6.5 km and 47 cm for the first event and 7 km and 72 cm for the second one, in good agreement with those derived from the seismological data.

Preseismic Creep Strains Revealed by Ground Tilt Measurements in Central Italy on the Occasion of the 1997 Umbria-Marche Apennines Earthquake Sequence

“…Fault slip for the two Colfiorito main shocks of September 26 reveals maximum amplitudes of 36 cm and 65 cm, respectively, as reported by HUNSTAD et al (1998) and STRAMONDO et al (1999). Although these shocks did not produce primary surface ruptures, the observed ground breaks (CINTI et al, 1999) identified a diffuse surface deformation along a 10-km-wide belt whose strike is in agreement with the The main shock occurred at 09:40 (M W ¼ 6.0; M 0 ¼ 1.26 · 10 25 dyne-cm) and accounts for about 50% of the total moment release in the sequence (EKSTRO¨M et al, 1998).…”

Coseismic and postseismic displacements related with the 1997 Earthquake Sequence in Umbria‐Marche (Central Italy)

“…Meghraoui et al [1999] suggested that the seismogenic low-angle normal faults were controlled by preexisting thrusts and branched at high-angle near the ground surface. Indeed, the analysis of DInSAR images [Stramondo et al 1999] and GPS measurements [Hunstad et al, 1999] suggest that the ruptures stopped very close to the surface.…”

Remote Sensing in Seismology: An Overview

“…At the same time, one of the four GPS benchmarks in the epicentral area measured about 14-cm horizontal and about 24-cm vertical movements. Either GPS or DInSAR has been the input data to an inversion modeling program that has provided an estimation of the fault parameters (Stramondo et al 1999) and the distribution of the slip over the fault plane (Fig. 4).…”