Introduction of the Coulomb stress on the optical fiber FBG for the probability of Earthquake as a Pre-cursors to Earthquakes


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.


Main Subjects

خواجوی، ر.، منوچهری، م. ف. و ریاحی، ع، 1382، الگوسازی توزیع تنش در گسل مسبب زمین‌لرزه 1382 بم با روش اجزای محدود، مرکز تحقیقات زمین‌لرزه‌شناسی دانشگاه فردوسی مشهد.
زارع، م، 1384، مقدمه‌ای بر زلزله‌شناسی کاربردی، مرکز چاپ و انتشارات وزارت امور خارجه، 75-85.
صالح‌زاده، ح، 1387، دایرۀ موهر و مسیر تنش در ژئو تکنیک، انتشارات دانشگاه علم صنعت ایران، 22–80.
Cocco. M and James R. Rice, “ Pore pressure and poroelasticity effects in Coulomb stress analysis of earthquake interactions “, JOURNAL OF GEOPHYSICAL RESEARCH, Vol. 107, pp. ESE.2.1-ESE.2.17, 2002.
Cocco. M, Nostro. C and Ekström.G, “Static stress changes and fault interaction during the 1997 Umbria-Marche earthquake sequence”, Journal of Seismology, Vol. 4, pp. 501–516, Oct 2000.
Gafsi. R, and El-Sherif. M. A, “Analysis of Induced-Birefringence effects on Fiber Bragg Gratings”, Optical Fiber Technology, Vol. 6 ,pp. 299-323, July 2000.
Kersey. A. D , Davis. M. A , Patrick . H. J , LeBlanc. M , Koo. K. P , Askins. C. G , Putnam. M. A , Joseph Friebele. E , “  Fiber Grating Sensors “ , JOURNAL OF LIGHTWAVE TECHNOLOGY, Vol. 15, pp. 1442-1463, Aug 1977.
King. C. P , Stein. Ross S , Lin. J , “ Static stress changes and the triggering of eatthquakes “ , Revised for Bull. Seismol. Soc. Am , Vol. 84, pp. 935-953, June 1994.
Liu. Q, Tokunaga. T and He. Z, “ Realization of nano static strain sensing with fiber Bragg gratings interrogated by narrow linewidth tunable lasers ” , Opt. Express, Vol. 19, pp. 20214-20223, Oct 2011.
M. Mirhabibi,  A. Negarestani, M. A. Bolorizadeh, M. R. Rezaei, A. Akhound, “A new approach for radon monitoring in soil as an earthquake precursor using optical fiber” , Journal of Radioanalytical and Nuclear Chemistry, Vol. 301, pp. 207-211, July 2014.
M. Talebian, J. Biggs, M. Bolourchi, A. Copley, A. Ghassemi, M. Ghorashi, J. Hollingsworth, J. Jackson, E. Nissen, B. Oveisi, B. Parsons, K. Priestley and A. Saiidi , “The Dahuiyeh (Zarand) earthquake of 2005 February 22 in central Iran: reactivation of an intramountain reverse fault “ , Geophys. J. Int, Vol. 164, pp. 137–148, 2006.
Terakawa. T , Zoporowski. A , Galvan.B , Miller. S. A, “  High-pressure fluid at hypocentral depths In The L'Aquila region inferred from earthquake focal mechanisms “, Geology. Gsapubs. Org , Vol. 38, pp. 995-998, Nov 2010.
Urban. F , Kadlec. J , Vlach. R , Kuchta. R , “ Design of a pressure sensor based on Optical Fiber Bragg Grating Lateral Deformation “ , ISSN, Vol. 10, pp. 11212–11225, Dec 2010.
Xu. M. G, Reekie. L, Chow. Y. T, and Dakin. J. P, “Optical in-fiber grating high pressure sensor”, Electron. Lett, vol. 29, pp. 398–399, Feb 1993.
Xu. M. G , Geiger. H , Dakin. J. P , “ Fiber grating pressure sensor with enhanced sensitivity using a glass-bubble housing ” , Electron. Lett. vol. 32 , pp. 128–129 , Jan 1996.
Zhang. Y , Feng. D , Liu. Z , Guo. Z , Dong. X , Chiang. K. S , Chu. B. C. B , “ High-sensitivity pressure sensor using a shielded polymer-coated fiber grating ” , IEEE Photon. Technol. Lett , vol. 13 , pp. 618–619 , June 2001.