@article { author = {توکلی, محمدرضا and امیری, حسین and نعمتی, مجید}, title = {Introduction of the Coulomb stress on the optical fiber FBG for the probability of Earthquake as a Pre-cursors to Earthquakes}, journal = {Journal of the Earth and Space Physics}, volume = {42}, number = {1}, pages = {15-24}, year = {2016}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2016.55104}, abstract = {Kuhbanan fault is in southeast margin of micro continent of Iran between Tabas and Yazd blocks. It directed from northwest of Kerman to northwest of Bahabad east of Bafgh (Yazd). Its length is about 300 km and its overall direction in Iran is in southeast – northwest. This fault has caused many historical deadly Earthquake and is recently more active at its southeast part near Zarand city. The most resent (2005) Earthquake of this fault costs 600 dead.We tried in this work to use specific parameters of this fault and stresses related to its Earthquakes for an attempt to Earthquakes prediction. Various methods have historically been used to find a way to Earthquake prediction. This has caused many researches to use different parameters in different ways. Although, there has been no considerable success except one or two cases, but attempts have opened many windows to search about. In this work, with respect to sensitivity of fiber optics to changes in physical parameters such as pressure and temperature, as a new approach we have theoretically investigated the possibility of using fiber optics in fault structure to find a precursor to seismic activities. In a special way, using Coulomb failure diagram and Mohr circle we could estimate stress distribution with time before the Earthquakes. The stress distribution around the focus of the quakes toward the surface inside the faults, where the cable may or can be used, was investigated. We fond from previous studies that there is no considerable differences between stresses at focal point and at points near surface. Depending on sensitivity of fiber optics to changes of pressure acting on and sensitivity of the cable to resulting changes of its length or its diameter, we found Bragg grating glass coated fiber is more useful to use in this range of stress changes. In such designed fibers the applied stresses will cause changes in the length of the fiber that is more effective in its sensitivity than changes in its diameter. As a reality, pre hazard stresses of the 2005 Zarand Earthquake related to the Kuhbanan fault structure, northern part of Kerman province (Iran), have been used to act on this kind of fibers to estimate changes in wavelength of output wave. This 2005 Earthquake of 6.4 magnitude, in Richter scale, has occurred two years and four months after the 2002 Earthquake of 5 magnitude in the same small area of Zarand. We could determine the increasing stresses between these two quakes in different times up to two days before the 2005 Earthquake. The stresses were applied to a glass coated fiber with a wave of 1550 nm wavelength passing through. As the stress is increasing during the time between the two quakes changes in wavelength (Δλ) increase toward a maximum value of 6.8 nm at the time of 2005 Earthquake. This value of Δλ is 6.57 nm 22 days and 6.16 nm about two months before the Earthquake, which are easily readable. That means in Kuhbanan fault structure when changes in output wavelength pass through 6.16 nm one should be careful.}, keywords = {Stress,Mohr’s circle,Coulomb failure,Bragg grating fiber optic,pre-cursors,earthquake prediction}, title_fa = {معرفی تنش‌های گسلی بر فیبرنوری FBGبرای بررسی امکان‌سنجی به عنوان یک پیش نشانگر برای زمین‌لرزه}, abstract_fa = {در این پژوهش با توجه به ویژگی فیبرنوری و حساسیتی که نسبت به تغییر پارامترهای فیزیکی نشان می‌دهد، به عنوان راهکاری جدید امکان استفاده از آن به عنوان پیش نشانگر لرزه‌ای در ساختار گسلی در سطح زمین مورد بررسی قرار گرفت. با استفاده از نمودار گسیختگی کولمب تنش‌های قبل از زمین لرزه با بکارگیری دایره موهر با روشی خاص تخمین زده شده است. با توجه به اینکه این تنش‌ها مربوط به کانون زمین لرزه در اعماق زمین می‌باشد، ابتدا لازم است چگونگی تغییرات تنش اطراف کانون به طرف سطح زمین (محل بکارگیری فیبر) مورد بررسی قرار گیرد. سپس با توجه به آستانه حساسیت فیبرهای نوری، فبیرنوری مبتنی بر توری براگ با تناوب کوتاه با پوشش حباب شیشه‌ای مناسب‌تر تشخیص داده شد. با اعمال تنش‌هایی که بتدریج و در نواحی سطحی گسل تجمیع می‌یابد تغییرات در طول موج نور خروجی محاسبه شده است. با توجه به فعالیت گسل کوهبنان واقع در شمال استان کرمان تنش‌های کولمب ناشی از چند زلزله این منطقه از جمله زلزله 2005 این گسل در زرند تقریباً از سه سال تا دو روز مانده به زمان زلزله تخمین و مورد استفاده قرار گرفته شد. مشاهده می‌شود که در این منطقه گسلی از حدود دو ماه مانده به رخداد جابجایی در طول موج نور خروجی از فیبرنوری از میزان 16/6 نانومتر و از 22 روز مانده به حادثه از 57/6 نانومتر عبور می‌کند، که می‌تواند زمان قابل توجهی برای هشدار باشد.}, keywords_fa = {تنش,دایره موهر,گسیختگی کولمب,فبیرنوری مبتنی بر توری براگ با تناوب کوتاه,اختلاف راه,پیش نشانگر لرزه ای}, url = {https://jesphys.ut.ac.ir/article_55104.html}, eprint = {https://jesphys.ut.ac.ir/article_55104_1f961100e5049e09638c1bbccf7952f9.pdf} }