A Barzegari; M Ghorashi; H Nazari; M.A Shokri; M Porkermani
Abstract
The north-south trending Astara Fault System (AFS) is located in the east of Talesh Mountains (TM) and west of the Caspian Sea. The probable seismic activity of this fault system will largely affect the north of GilanProvince. The AFS is one of the basement faults in Iran, which plays an important role ...
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The north-south trending Astara Fault System (AFS) is located in the east of Talesh Mountains (TM) and west of the Caspian Sea. The probable seismic activity of this fault system will largely affect the north of GilanProvince. The AFS is one of the basement faults in Iran, which plays an important role in TaleshMountains region and subsidence of the South Caspian Basin (SCB). It seems that the AFS is the source of moderate to large magnitude instrumental earthquakes such as the 16-4-1913 (Magnitude=5.1), 11-7-1970 (Magnitude Mb=5.2), 4-11-1978 (Magnitude Ms=6.0) earthquakes.However, little is known about historical earthquakes related to the AFS, but it has been probably the source of the 1709AD and 1713AD historical earthquakes in Rasht. In spite of the earthquakes attributed to the AFS, the lack of critical seismic information such as recurrence interval, slip rate and activity rate of the AFS has made its future seismic activity ambiguous. This research aims at assessing the earthquake recurrence interval related to the AFS. Therefore, two different methods, i.e. Gutenberg–Richter and Kijko–Sellovelmethods,were used to estimate the recurrence interval. The results obtained from the Gutenberg–Richter method represent anearthquake of Ms>8 to occur in the interval of 500, 1000 and 2000 years. The results of the Kijko–Sellovel method, however, representearthquakes with the magnitudes of Ms =7.3, Ms =7.7 andMs =7.9 to occur in the interval of 500, 1000 and 2000 years, respectively.
M. Basiri; H. Nazari; M. Foroutan; S. Solaymani Azad; M. A. Shokri; M. Talebian; M. Ghorashi; M. J. Bolourchi; A. Rashidi
Abstract
The Golbaf area in Kerman province (SE Iran) has experienced five earthquake of Mw 5.4-7.1 between 1981 and 1998. Occurrences of these earthquakes in seventeen years time interval indicate that occurrences of earthquakes on the Golbaf (Gowk) fault system have a clustering model. In this study we use ...
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The Golbaf area in Kerman province (SE Iran) has experienced five earthquake of Mw 5.4-7.1 between 1981 and 1998. Occurrences of these earthquakes in seventeen years time interval indicate that occurrences of earthquakes on the Golbaf (Gowk) fault system have a clustering model. In this study we use morphotectonical and paleoseismological evidences to show that seismic behavior of this fault in the past has a clustering model in some time intervals. For this purpose at the first near-field morphotectonical analysis performed using real time kinematics (RTK) GPS survey and digital elevation model and digital topographic map of surface ruptures of past earthquake prepared with high accuracy. Detail analyzing of this model indicate that the rake angle of Golbaf fault is about 10 degree. This result is in agreement with rake angle calculated from seismological methods and also observations of slickenlines on rupture plans that show dominant right lateral strike slip mechanism of the Golbaf fault. According to the paleoseismological investigations which were associated with digging a trench perpendicular to the Golbaf fault indentified four Paleoearthquake with magnitudes of Mw>6.6. By using some of empirical relationship, maximum magnitude of oldest Paleoearthquake calculated about Mw 8.2 that it is unbelievable and show similar to today that occurred five earthquake during short time interval on this fault, occurrence of earthquake in the past on some of time interval have clustering model so that occurred a lot of big earthquake in short time interval that there was not enough opportunity for sedimentation and record of evidences of this earthquake separately.
M. Shokri; M. Ghorashi; H. Nazari; R. Salamati; M. Talebian; J.-F. Ritz; H. Mohammad khani; M. Shahpasand zadeh
Abstract
The Astaneh fault with a length of more than 75 km is located in NW of Damghan. Morphotectonic investigation along the Astaneh fault and left - lateral displacement in quaternary deposits shows that, Astaneh is an active fault. It is necessary to recognize paleoseismicity of Astaneh fault because, this ...
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The Astaneh fault with a length of more than 75 km is located in NW of Damghan. Morphotectonic investigation along the Astaneh fault and left - lateral displacement in quaternary deposits shows that, Astaneh is an active fault. It is necessary to recognize paleoseismicity of Astaneh fault because, this fault is located in seismic zone of Komes historical earthquake with Ms=7.9 (Ambraseys & Melville, 1982). Many people (more than 45000) were killed in Damghan city in Komes historical earthquake. In this paper, 4-5 paleo events along the Astaneh fault are presented through paleoseismological investigation.
