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Ghafory-Ashtiany, M.
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Ghafory-Ashtiany, M.
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- PublicationRestrictedA geologic contribution to the evaluation of the seismic potential of the Kahrizak fault (Tehran, Iran)(1998-03-20)
; ; ; ; ; ; ;De Martini, P. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Hessami, K.; International Institute of Earthquake Engineering and Seismology, Tehran, Iran ;Pantosti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;D'Addezio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Alinaghi, H.; International Institute of Earthquake Engineering and Seismology, Tehran, Iran ;Ghafory-Ashtiani, M.; International Institute of Earthquake Engineering and Seismology, Tehran, Iran; ; ; ; ; In this paper we present the results of preliminary geomorphic and trenching investigations along the Kahrizak fault. This fault is located south of the highly populated metropolis of Tehran and represents one of the main structures in the area containing important seismic potential. The Kahrizak fault has a very clear expression at the surface where it forms a prominent 35-km-long, 15-m-high scarp on Holocene alluvial deposits. The fault strikes N70°-80°W and dips to the north. Movement is prevalently right-lateral with the northern side of the fault up. Trench excavations exposed a sequence of weathered, massive, alluvial deposits which are dated, by means of radiometric methods, to the Holocene. In the trenches the sequence is intensely deformed by north-dipping, high- and low-angle faults within a 30-m-wide zone. On the basis of stratigraphic and structural relations, some evidence for individual Holocene earthquakes is found; however, we were not able to reconstruct the seismic history of the fault nor to evaluate the size of deformation produced by each event. Because of the possible ~10 m offset of ancient linear hydraulic artifacts (qanáts), that cross the fault, we hypothesize that the most recent event may have occurred in historical times (more recent than 5000 yr B.P.) and it may be one of those reported in this area by the current catalogues of seismicity. Based on these preliminary investigations we estimate an elapsed time between 5000 and 800 years, a maximum slip per event dmax of ~10 m, a minimum Holocene vertical slip rate of ~1 mm/yr versus a horizontal slip rate of ~3.5 mm/yr, a maximum of ~3000 years for the average recurrence time, and an expected Mw = 7.0 to 7.4. These can be considered as a first-hand reference for the activity on this fault.221 32 - PublicationOpen AccessSeismic hazard assessment of Iran(1999-12)
; ; ;Tavakoli, B.; International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, I.R. Iran ;Ghafory-Ashtiany, M.; International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, I.R. Iran; The development of the new seismic hazard map of Iran is based on probabilistic seismic hazard computation using the historical earthquakes data, geology, tectonics, fault activity and seismic source models in Iran. These maps have been prepared to indicate the earthquake hazard of Iran in the form of iso-acceleration contour lines, and seismic hazard zoning, by using current probabilistic procedures. They display the probabilistic estimates of Peak Ground Acceleration (PGA) for the return periods of 75 and 475 years. The maps have been divided into intervals of 0.25 degrees in both latitudinal and longitudinal directions to calculate the peak ground acceleration values at each grid point and draw the seismic hazard curves. The results presented in this study will provide the basis for the preparation of seismic risk maps, the estimation of earthquake insurance premiums, and the preliminary site evaluation of critical facilities.1078 1579 - PublicationOpen AccessSeismic hazard assessment for the Caucasus test area(1999-12)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Balassanian, S.; National Survey for Seismic Protection, Yerevan, Armenia ;Ashirov, T.; Institute of Seismology, Academy of Sciences, Ashkhabad, Turkmenistan ;Chelidze, T.; Institute of Geophysics, Academy of Sciences, Tbilisi, Georgia ;Gassanov, A.; Experimental Methodical Geophysical Expedition, Academy of Sciences, Baku, Azerbaijan ;Kondorskaya, N.; Joint Institute of Physics of the Earth, Moscow, Russia ;Molchan, G.; International Institute of Earthquake Prediction Theory and Mathematical Geophysics, Moscow, Russia ;Pustovitenko, B.; Geophysics Institute, National Academy of Sciences, Kiev, Ukraine ;Trifonov, V.; Joint Institute of Physics of the Earth, Moscow, Russia ;Ulomov, V.; Joint Institute of Physics of the Earth, Moscow, Russia ;Giardini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Erdik, M.; Bogazici University, Kandilli Observatory, Istanbul, Turkey ;Ghafory-Ashtiany, M.; International Institute of Earthquake Engineering and Seismology, Teheran, Iran ;Grünthal, G.; GeoForschungsZentrum, Potsdam, Germany ;Mayer-Rosa, D.; Institute of Geophysics, ETH Zurich, Switzerland ;Schenk, V.; Institute of Rock Mechanics, Academy of Sciences, Prague, Czech Republic ;Stucchi, M.; Istituto di Ricerca sul Rischio Sismico, Milano, Italy; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The GSHAP CAUCAS test area was established under the INTAS Ct.94-1644 (Test Area for sismic Hazard Assessment in the Caucasus) and NATO ARW Ct.95-1521 (Historical and Prehistorical Earthquakes in the Caucasus), with the initial support of IASPEI, UNESCO and ILP. The high tectonic interest and seismicity rate of the whole area, the availability of abundant multi-disciplinary data and the long established tradition in hazard assessment provide a unique opportunity to test different methodologies in a common test area and attempt to establish some consensus in the scientific community. Starting from the same input data (historical and instrumental seismic catalogue, lineament and homogeneous seismic source models) six independent approaches to seismic hazard assessment have been used, ranging from pure historical deterministic to seismotectonic probabilistic and areal assessment methodologies. The results are here compared.881 482