بازسازي ميدان تنش محلي امروزي مؤثر بر گسل شمال تبريز و مناطق پيرامون آن براساس سازوكاز كانوني زلزله¬ها با استفاده از روش وارون

Reconstruction of present-day local stress field affecting the North Tabriz Fault and surrounding areas based on earthquakes focal mechanism by using inversion method

در اين مطالعه، ميدان تنش زمين¬ساختي امروزي مؤثر بر گسل شمال تبريز و نواحي پيرامون آن با استفاده از 37 سازوكار كانوني زلزله¬هاي جمع آوري شده از منابع مختلف، بازسازي شده است. براي تعيين ماهيت سازوكار كانوني زلزله¬ها و دامنه تغييرات ماهيت آن¬ها در رژيم¬هاي مختلف زمين¬ساختي از نمودارهاي مثلثي استفاده شده است. ماهيت سازوكار اين داده¬ها از رژيم امتدادلغزي تا راندگي تغيير مي¬كند. براي به دست آوردن تنسورهاي تنش تقليل يافته¬اي كه بيشترين تعداد داده¬ها در آن شركت كنند و ميدان¬هاي بازسازي شده، پوشش كاملي نسبت به تنش¬هاي مؤثر بر منطقه داشته باشد، فرايند جدايش تنش¬ها برروي داده¬ها براي جداسازي رژيم¬هاي زمين¬ساختي متفاوت از سيستم چند مرحله¬اي اعمال شد. نتايج تحليل وارون و جدايش داخلي داده¬ها، نشان مي¬دهد در اين منطقه سه سامانه تنش عمل مي¬كنند. به‌طور جالب توجهي هر سه سامانه تنش داراي جهت فشارش افقي در جهت شمال غرب-جنوب شرق تا شمال شمال غرب-جنوب جنوب شرق هستند. جهت بيشينه فشارش در هر كدام از رژيم¬هاي تنش اول، دوم و سوم به ترتيب 329/09، 310/28 و 138/03 مي¬باشد.

In this research, present-day tectonic stress field affecting North Tabriz Fault and surrounding areas was reconstructed by using 37 compiled earthquakes focal mechanism from various sources. Triangle diagrams were used to determine the sense of the earthquakes focal mechanism. The sense of these data varies from strike-slip to thrust regime. Stress separation process was applied on data set for separation of the various tectonics regimes from a poly-phase system to obtain reduced stress tensors. This was done because most of the data participated in them and reconstructed stress fields completely cover the stresses affecting the region. The results of inversion analysis and internal separation of the data set show three stress regimes acting in this region. Considerably, all three stress regimes have a horizontal pressure stress with NW-SE to NNW-SSE trend. The direction of maximum pressure in each first, second and third regimes is 09/329, 28/310 and 03/138, respectively. In this research, present-day tectonic stress field affecting North Tabriz Fault and surrounding areas was reconstructed by using 37 compiled earthquakes focal mechanism from various sources. Triangle diagrams were used to determine the sense of the earthquakes focal mechanism. The sense of these data varies from strike-slip to thrust regime. Stress separation process was applied on data set for separation of the various tectonics regimes from a poly-phase system to obtain reduced stress tensors. This was done because most of the data participated in them and reconstructed stress fields completely cover the stresses affecting the region. The results of inversion analysis and internal separation of the data set show three stress regimes acting in this region. Considerably, all three stress regimes have a horizontal pressure stress with NW-SE to NNW-SSE trend. The direction of maximum pressure in each first, second and third regimes is 09/329, 28/310 and 03/138, respectively.