The 2003 Bam (SE Iran) earthquake: precise source parameters from satellite radar interferometry

Abstract

S U M M A R YDifferential radar interferometry provided high-quality near-field deformation data for the 2003 Bam earthquake and therefore strong constraints on its source parameters. The ruptured fault segments could be clearly detected by using a Sobel Edge Filter on the phase-unwrapped deformation field. The estimated total rupture length is about 24 km. More than 80 per cent of the seismic moment was released from its southern segment of about 13 km, where the slip reached a maximum of up to 270 cm resulting in a stress drop of at least 6 MPa. In addition, optical remote sensing data show that the Bam fault is not a single fault but consists of a 4-5 km wide fault system with the known main branch running between the city of Bam and Baravat. The fault ruptured by the Bam earthquake appears to continue the NW branch of this fault system from Bam city southwards. Based on these results, we suggest that the Bam earthquake ruptured a hidden or new fault and that in this process an unusually strong asperity was involved.

Combination of Precise Leveling and InSAR Data to Constrain Source Parameters of the Mw = 6.5, 26 December 2003 Bam Earthquake

“…The main strike-slip dislocation in TALEBIAN et al (2004) is located approximately 5 km west of the previously-mapped Bam fault, while the surface projection of the secondary dislocation lies at a distance of about 10 km east of the main rupture. WANG et al (2004) used descending and ascending interferograms and constructed a source model based on three rectangular faults, rupturing a total length of about 24 km from south to north crossing the Bam city. WANG et al (2004) concluded that more than 80 percent of seismic moment was released from a new dislocation located 4-5 km west of the Bam fault dipping 80°E.…”

“…WANG et al (2004) used descending and ascending interferograms and constructed a source model based on three rectangular faults, rupturing a total length of about 24 km from south to north crossing the Bam city. WANG et al (2004) concluded that more than 80 percent of seismic moment was released from a new dislocation located 4-5 km west of the Bam fault dipping 80°E. WANG et al (2004) found no evidence for secondary thrust dislocation as proposed by TALEBIAN et al (2004).…”

“…TALEBIAN et al (2004) examined Envisat ASAR data in descending orbit and argued that a combination of two mechanisms is necessary to fit InSAR observations; a vertical strike-slip dislocation approximately 5 km west of the Bam fault and a pure thrust dislocation beneath the Bam fault. WANG et al (2004) inverted descending and ascending interferograms and concluded that the Bam event was a right-lateral strike-slip earthquake that ruptured a total length of about 24 km from south to north crossing the Bam city. WANG et al (2004) found no evidence for secondary thrust dislocation as proposed by TALEBIAN et al (2004).…”

“…WANG et al (2004) inverted descending and ascending interferograms and concluded that the Bam event was a right-lateral strike-slip earthquake that ruptured a total length of about 24 km from south to north crossing the Bam city. WANG et al (2004) found no evidence for secondary thrust dislocation as proposed by TALEBIAN et al (2004).…”

Slip model of the 2008 M w 7.9 Wenchuan (China) earthquake derived from co-seismic GPS data

“…We derive the slip distribution from the co-seismic GPS data using the inversion code SBIF (sensitivity-based iterative fitting) proposed by Wang et al (2006). The technique used in this code is similar to the constrained gradient approach as used by Ward and Barrientos (1986) to minimize the misfit function under a priori constraints.…”