TY - JOUR A1 - Donner, Stefanie A1 - Rößler, Dirk A1 - Krüger, Frank A1 - Ghods, Abdolreza A1 - Strecker, Manfred T1 - Segmented seismicity of the M (w) 6.2 Baladeh earthquake sequence (Alborz Mountains, Iran) revealed from regional moment tensors JF - Journal of seismology N2 - 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) a parts per thousand yen3.3) 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 28A degrees south-dipping area of 24 x 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 85A degrees towards the north. KW - Alborz Mountains KW - Iran KW - Baladeh earthquake KW - Inversion for moment tensors KW - Seismotectonics Y1 - 2013 U6 - https://doi.org/10.1007/s10950-013-9362-7 SN - 1383-4649 VL - 17 IS - 3 SP - 925 EP - 959 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Landgraf, Angela A1 - Zielke, Olaf A1 - Arrowsmith, J. Ramón A1 - Ballato, Paolo A1 - Strecker, Manfred A1 - Schildgen, Taylor F. A1 - Friedrich, Anke M. A1 - Tabatabaei, Sayyed-Hassan T1 - Differentiating simple and composite tectonic landscapes using numerical fault slip modeling with an example from the south central Alborz Mountains, Iran JF - Journal of geophysical research : Earth surface N2 - The tectonically driven growth of mountains reflects the characteristics of the underlying fault systems and the applied tectonic forces. Over time, fault networks might be relatively static, but stress conditions could change and result in variations in fault slip orientation. Such a tectonic landscape would transition from a simple to a composite state: the topography of simple landscapes is correlated with a single set of tectonic boundary conditions, while composite landscapes contain inherited topography due to earlier deformation under different boundary conditions. We use fault interaction modeling to compare vertical displacement fields with topographic metrics to differentiate the two types of landscapes. By successively rotating the axis of maximum horizontal stress, we produce a suite of vertical displacement fields for comparison with real landscapes. We apply this model to a transpressional duplex in the south central Alborz Mountains of Iran, where NW oriented compression was superseded by neotectonic NE compression. The consistency between the modeled displacement field and real landforms indicates that the duplex topography is mostly compatible with the modern boundary conditions, but might include a small remnant from the earlier deformation phase. Our approach is applicable for various tectonic settings and represents an approach to identify the changing boundary conditions that produce composite landscapes. It may be particularly useful for identifying changes that occurred in regions where river profiles may no longer record a signal of the change or where the spatial pattern of uplift is complex. KW - fault interaction KW - landscape evolution KW - numerical modeling KW - Alborz Mountains KW - Iran Y1 - 2013 U6 - https://doi.org/10.1002/jgrf.20109 SN - 2169-9003 SN - 2169-9011 VL - 118 IS - 3 SP - 1792 EP - 1805 PB - American Geophysical Union CY - Washington ER -