نوع مقاله : مقاله پژوهشی

نویسندگان

• علی حسنخانی ¹
• مهدی مدیری ²
• احمد نقوی ³

¹ کارشناس ارشد ژئوفیزیک - مهندسی زلزله

² استاد دانشگاه صنعتی مالک اشتر

³ کارشناس ارشد هوش مصنوعی

چکیده

شبیه‌سازی جنبش نیرومند زمین به ویژه برای مناطقی که از آن‌ها داده‌ای در دسترس نیست، نقش مهمی در برآورد پارامترهای جنبش نیرومند زمین ایفا می‌کند. یکی از روش‌های بررسی زمین لرزه‌ها با استفاده از شتابنگاشت ها، شبیه‌سازی جنبش نیرومند زمین است. با معرفی دو مدل شبیه‌سازی تعینی(اجزای محدود- عدد موج گسسته[1] و گسل محدود که صحت سنجی و اعتبار سنجی آنها مورد بررسی قرار گرفته است، برای رخدادهای حوزه نزدیک (فاصله کمتر از 20 کیلومتر تا گسل مسبب) و دور ازگسل، نگاشت های شبیه‌سازی شده  تولید، و روابط کاهندگی و پارامترهای جنبش نیرومند زمین برای ایالت لرزه زمین ساختی زاگرس ارایه شده اند.
به‌منظور تعیین پارامترهای کلیدی ورودی شبیه‌سازی، مطالعات معتبر صورت‌گرفته زمین‌شناسی و لرزه‌شناسی مربوط به ناحیه لرزه‌خیز زاگرس، مورد استفاده قرار گرفته است. برای تولید بانک اطلاعاتی جامع تعداد زیادی ایستگاه فرضی در زوایای مختلف در اطراف گسل لحاظ شد. با در نظرگرفتن پارامترهای زلزله‌شناسی منطقه، حدود 20000 شتابنگاشت مصنوعی تولید شده است. روابط کاهندگی ارایه شده بر اساس تحلیل نتایج پارامترهای بیشینه شتاب زمین[2] و دامنه پالس با روابط معتبر جهانی و روابط ارائه شده برای ایالت لرزه زمین ساختی زاگرس مورد مقایسه قرار گرفته و همخوانی (درصد تطابق) قابل قبولی با آن‌ها نشان می‌دهد.
این روابط می‌توانند چشم انداز تازه ای در مکانیابی ها، بررسی رفتار دینامیکی سازه ها و توسعه زیرساخت های مختلف در راستای کاهش حداکثری و پیش بینی خسارات ناشی از زلزله ارایه دهند.
 
[1] Finite fault-Discrete wave number
[2] PGA(Peak Ground Acceleration)

کلیدواژه‌ها

• شبیه‌سازی جنبش نیرومند زمین
• حوزه نزدیک و دور گسل
• ایالت لرزه زمین ساختی
• رابطه کاهندگی

موضوعات

• استخراج، پردازش، تولید و نمایش داده های جغرافیایی

عنوان مقاله [English]

Presenting Attenuation relations for near and far field fault zone events using two simulation methods for the Zagros seismotectonic earthquake region

نویسندگان [English]

• Ali Hasankhani ¹
• Mahdi Modiri ²
• Ahmad Naghavi ³

¹ Master's Degree in Geophysics-Earthquake Engineering

² Professor of Malek Ashtar University of Technology

³ Master’s Degree in Artificial Intelligence

چکیده [English]

Extended Abstract
Introduction
Unfortunately, it is worth noting that the maximum of fifty years of record history around the world does not include all the wave propagation conditions in the environment, the type of construction, the rupture process on the fault, and the geometrical relationship between the construction and the fault.
Especially in the areas close to the fault, this problem is more seen. Before the 1999 Chichi earthquake in Taiwan and the 1999 Izmit earthquake in Turkey, there were only about 20 records of earthquakes with a magnitude greater than 7 at a distance of less than 20 kilometers from the fault.
The Turkish earthquake added 5 records and the Taiwan earthquake added 65 records to this collection, but only two fault rupture scenarios were added to our knowledge, while thousands of other possible scenarios may occur. This issue led seismologists and earthquake engineers to try to estimate the parameters related to the strong motion of the earth in the area near the fault with an acceptable confidence factor using various simulation methods, both experimental and theoretical.
Methods
In a general classification in engineering seismology, the methods of investigation and analysis of the earthquake phenomenon and the resulting movements are divided into two categories: dynamic and kinematic. Based on this, seismological models and problems are divided into two categories. Kinematic models are the ones based on slip distribution that do not take into account the state of stress on the fault. While in dynamic models, we deal with the physics of fault rupture and its causes.
On the other hand in another point of view, simulation methods are divided into three main categories: deterministic (low frequencies), stochastic (high frequencies) and hybrid (broad band) methods.
On the whole Simulation of strong ground motion, especially for regions where they are not available, plays an important role in estimating the parameters of the strong ground motions. One of the methods of examining earthquakes using the acceleration of mapping is to simulate the powerful earth movement. Introducing two decisive simulation models (Discrete Wave Number Finite Fault) and Finite Faults, which are investigated and validated, for close-up events (less than 20 km to a seismogenic fault.) And far away, how the simulated recording are produced, the supply of reduction relationships for the Zagros seismotectonics region, and consequently the forecast of the strong motions parameters.
 Results & Discussion
Due to the special geological conditions and the existence of many active faults in Iran, our country is considered one of the earthquake-prone regions of the world. Not all places in Iran are equally prone to earthquakes. The most seismic region of Iran (which has the highest number of earthquakes) is the Zagros region. The modeling method based on finite fault combines the aspects of plane source with the ground motion model based on point source and since the mentioned limitations are not naturally present in the modeling method based on finite fault, this method takes into account the geometry of the failure and the directivity effect and good results are obtained. For simulation using finite fault, the method of time delay and acceleration summation of maps related to a two-dimensional network including elements is used.
In this method, the fault plane is divided into elements and a small event is simulated for each one, and finally at the recording station, the overall recording acceleration is obtained from the sum of the effects of small events. The strong ground motions in each micro-fault are calculated using the random point spring method and then summed at the desired point with an appropriate time delay to obtain the ground motion of the entire fault.
To determine the key parameters of the simulation input, valid geological and seismic studies are used in each state of seismic. To produce a comprehensive database of simulated records, a significant number of stations are taken into account with different hypotheses around the fault, and the acceleration of artificial mapping has been produced by the region’s seismological parameters. In the next step, with the selection of the appropriate functional , the appropriate reduction relationship is suitable. The results of the simulation as well as the resulting relationship are compared with the results extracted from the valid global  attenuation relationships and the relationships provided for the area in question and their consistency (compliance percentage) is investigated.
Conclusion
In this research, we have produced a wide range of simulated records (about 20 thousand records) for the Zagros seismotectonics region. We hope that the relationships obtained will have sufficient accuracy and efficiency and be used in the design of structures and urban development. It is important to mention that the regression correlation coefficient (R-Square) was above 0.95 in all the fits.
These attenuation relationships can provide a new perspective on site location, the dynamic behavior of structures, and the development of various infrastructure in order to reduce the maximum and predict the damage caused by earthquakes.

کلیدواژه‌ها [English]

• Earthquake
• Seismological models
• Strong ground motion simulation
• Finite fault
• Attenuation relationships
• Zagros
• Site location