Active transtension inside central Alborz: A new insight into northern Iran–southern Caspian geodynamics

Ritz, Jean‐François; Nazari, Hamid; Ghassemi, A.; Salamati, Reza; Shafei, A.; Solaymani, Shahryar; Vernant, Philippe

doi:10.1130/g22319.1

Cited by 206 publications

(150 citation statements)

References 12 publications

(18 reference statements)

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“…9). The Mosha Fasham fault is well studied by microseismic, paleoseismic, and morphotectonic surveys (Ashtari et al, 2005;Ritz et al, 2006;Landgraf et al, 2009;Tatar et al, 2012). The kinematics of the Mosha Fasham fault is linked with the north Tehran thrust fault further west.…”

Section: Discussionmentioning

confidence: 99%

Combined Inversion of Broadband and Short-Period Waveform Data for Regional Moment Tensors: A Case Study in the Alborz Mountains, Iran

Donner

Rössler

Ghods

2014

Bulletin of the Seismological Society of America

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In this study, we suggest a novel approach for the retrieval of regional moment tensors for earthquakes with small to moderate magnitudes. The first modification is the combined inversion of broadband and short-period waveform data. The broadband waveforms are inverted in a frequency range suitable for surface waves, whereas for the short-period data a frequency range suitable for body waves is applied. The second modification is the use of first-motion body-wave polarities to select the most probable solution out of all solutions from inversion. To combine three different criteria for selecting the most probable solution (i.e., residual from inversion, doublecouple content of solution, number of nonmatching first-motion body-wave polarities), the L2 norm is applied to the normalized parameters. We chose five earthquakes within the Alborz mountains, Iran, as a case study (3:1 ≤ M w ≤ 4:1). In this area, several factors exacerbate the difficulty of performing inversion for moment tensors, for example, a heterogeneous station network and large azimuthal gaps. We have demonstrated that our approach supplies reliable moment tensors when inversion from broadband data alone fails. In one case, we successfully retrieved a stable solution from short-period waveform data alone. Thus, our approach enables successful determination of seismic moment tensors wherever a sparse network of broadband stations has thus far prevented it.

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Section: Discussionmentioning

confidence: 99%

Combined Inversion of Broadband and Short-Period Waveform Data for Regional Moment Tensors: A Case Study in the Alborz Mountains, Iran

Donner

Rössler

Ghods

2014

Bulletin of the Seismological Society of America

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“…The magnetic parameters are taken from the recent magnetic survey conducted in the Mosha fault region (Mokhtari et al, 2008). The other main parameters of the fault are based on Ashtari et al (2005), Moinabadi and Yassaghi (2007), Ritz et al (2006) and Guest et al (2006) given in Table 2. Using the computer program developed during this study, both declination and inclination changes along the Mosha fault have been examined.…”

Section: Numerical Examplesmentioning

confidence: 99%

The pattern and magnitude of rotational piezomagnetic anomalies along the dip-slip Mosha fault, Northern Tehran, Iran

Mokhtari

Kiarasi

2008

Nat. Hazards Earth Syst. Sci.

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Abstract. Several active faults affect the Central Alborz, Northern Iran. The main active faults in the region are the North Tehran and the Mosha faults and their westward continuation, the Taleghan fault. Among these the Mosha fault is the most active fault in Central Alborz. The piezomagnetic field has been inspired by many investigations in the earthquake prediction studies and has been reported in the literature. Several theories proposed for relating piezomagnetic changes into magnetic signals accompanying earthquakes in the vicinity of a fault. In this study based on an analytical solution for the elementary piezomagnetic potentials due to an inclined rectangular fault within a semi-infinite elastic medium a computer program has been developed. This program has been used for evaluation of the rotational piezomagnetic changes along the Mosha fault using different earthquakes with specific magnitudes and at the presence of three different geomagnetic main fields. The magnetic data acquired recently at the study area has been used during the modeling. The first result that can be inferred from this study is that rotational piezomagnetic anomalies are completely localized at the fault tips. So for detection of this anomaly the magnetic instruments should be installed at these locations. The other important element which has been investigated was the amount of slip along the fault, which shows anomaly intensification by increase in the amount of slip.

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“…Ambraseys and Melville, 1982;Berberian and Yeats, 1999) and the active tectonics features observed along them (e.g. Berberian et al, 1985;Trifonov et al, 1996;Solaymani et al, 2003;Ritz et al, 2006). Berberian et al, 1985 attributed the 4 B.C.…”

Section: Introductionsmentioning

confidence: 99%

Employing Minimum age model (MAM) and Finite mixture modeling (FMM) for OSL age determination of two important samples from Ira Trench of North Tehran Fault

2016

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Ira trench site is in a point where, the surface trace of North Tehran Fault (NTF) joins the Mosha Fault (MF) in the north-eastern margin of Tehran and can provide important paleosismological information for Tehran. The Ira trench, were divided into 6 packages (I to VI), described, according to their composition, relative and absolute ages. Package I consists of units 23, 25, 26, 27, 28, 29, 30 and 31. The whole package I mainly belongs to Holocene, and provides essential constraints for the recent paleo-earthquake activity of the EMF and NTF zone. Therefore, finding accurate ages for the units of this package is very important. Three colluvial wedges (units 23, 26, 28) are present between 20 and 36.5 m north in package I, which are assigned to 3 episodes of activity on Fault 13. Central age model (CAM) provided OSL ages of 35.0 ± 6.1, 7.3 ± 1.3, 6.4 ± 0.9 and 56 ± 6.5 ka for units 23, 26, 28 and 29, respectively. The conflicting ages of 56 ± 6.5 and 35.0 ± 6.1 ka (for units 23 and 29, respectively) as compared to the underlying younger units suggest that these ages are overestimated. MAM provided OSL ages of 13.1 ± 4.3 and 3.5 ± 0.4 ka for units 23 and 29, respectively. The contribution of the new statistical age model of sample IRA4 to the paleoseismic data is discussed.

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Active transtension inside central Alborz: A new insight into northern Iran–southern Caspian geodynamics

Cited by 206 publications

References 12 publications

Combined Inversion of Broadband and Short-Period Waveform Data for Regional Moment Tensors: A Case Study in the Alborz Mountains, Iran

Combined Inversion of Broadband and Short-Period Waveform Data for Regional Moment Tensors: A Case Study in the Alborz Mountains, Iran

The pattern and magnitude of rotational piezomagnetic anomalies along the dip-slip Mosha fault, Northern Tehran, Iran

Employing Minimum age model (MAM) and Finite mixture modeling (FMM) for OSL age determination of two important samples from Ira Trench of North Tehran Fault

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