Segmented seismicity of the Mw 6.2 Baladeh earthquake sequence (Alborz mountains, Iran) revealed from regional moment tensors

Stefanie Donner, Dirk Rössler, Frank Krüger, Abdolreza Ghods, Manfred R. Strecker

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The M w 6.2 Baladeh earthquake occurred on 28 May 2004 in the Alborz Mountains, northern Iran. This earthquake was the first strong shock in this intracontinental orogen for which digital regional broadband data are available. The Baladeh event provides a rare opportunity to study fault geometry and ongoing deformation processes using modern seismological methods. A joint inversion for hypocentres and a velocity model plus a surface-wave group dispersion curve analysis were used to obtain an adapted velocity model, customised for mid- and long-period waveform modelling. Based on the new velocity model, regional waveform data of the mainshock and larger aftershocks (M w  ≥3.3) were inverted for moment tensors. For the Baladeh mainshock, this included inversion for kinematic parameters. All analysed earthquakes show dominant thrust mechanisms at depths between 14 and 26 km, with NW–SE striking fault planes. The mainshock ruptured a 28° south-dipping area of 24 × 21 km along a north-easterly direction. The rupture plane of the mainshock does not coincide with the aftershock distribution, neither in map view nor with respect to depth. The considered aftershocks form two main clusters. The eastern cluster is associated with the mainshock. The western cluster does not appear to be connected with the rupture plane of the mainshock but, instead, indicates a second activated fault plane dipping at 85° towards the north.
Original languageEnglish
JournalJournal of Seismology
Volume17
Issue number3
Pages (from-to)925-959
Number of pages35
ISSN1383-4649
DOIs
Publication statusPublished - 2013

Keywords

  • Alborz mountains
  • Iran
  • Baladeh earthquake
  • Inversion for moment tensors
  • Seismotectonics

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