Slip rate partitioning in the fault system of NW Iranian plateau based on GPS observations

Document Type : Research Article

Author

Department of Surveying, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran.

Abstract

Fault slip rate distribution plays an important role in earthquake studies. Faults are loaded at very slow rates in continental interiors. So, interaction among faults and resulting slip distribution can give rise to earthquakes on other faults after a long period of quiescence and seismicity that can migrate from one fault to the onother one.
NW Iran-Eastern Turkey is a region of active deformation as a result of oblique collision of Arabia-Eurasia tectonic plates. In northwestof Iran, deformation between the Central Iranian block and the Caucasus domain is accommodated by a fault system and mainly by right lateral strike-slip on the North Tabriz fault. In the current study, we did slip rate partitioning in the fault system of northwest Iranian plateau using the concepts of dislocation theory. Modelling approach is described by Gomberg and Ellis (1994), Flerit et al., (2003) and Armijo et al., (2004) and it differs from rigid block models (Reilinger et al., 2006; Djamour et al., 2011) in which dislocation conditions at the boundaries of blocks are often incompatible with geological evidences. In the alternative method of Flerit et al., (2003), slip everywhere has a direction of motion consistent with geological constraints. The dislocations do not divide the region into closed rigid blocks and slip can vary along strike as observed geologically. Finally we obtain a tectonic model for NW Iran-Eastern Turkey that is more realistic than rigid block model (Reilinger et al., 2006; Djamour et al., 2011) or models based on seismic or geologic strain rates (Haines, 1982; Haines and Holt, 1993; Jackson et al., 1995; Masson et al., 2005). For this purpose we use a three dimensional boundary elements method. 
First, we consider an elastic and homogeneous half-space for the study area. Then geometric data of fault system are collected from geological and geophysical sources including fault length, width, dip, and locking depth. For Lame coefficients, we use global average values. Both mentioned geometrical and physical data are kept fixed in the modeling process. Then, strain tensor that best fits the GPS data is estimated for the study area using least squares method. Then, stress rate tensor is estimated using generalized Hook’s law. Geomerical chracteristics of faults, physical characteristics of crust and stress rate tensor act as boundary conditions in the model.
Faults are locked in normal direction but they are allowed to slip freely in strike and dip directions under the influence of boundary conditions. Regarding the strike changes of faults, the fault surfaces are divided by different segments in strike direction with constant strikes and dips. Then fault segment surfaces are divided into 1km elements. Finally, we have free slipping elements in strike and dip directions as inputs for modeling.
Our model is fitted to the fault traces data set of NW Iran-eastern Turkey. The results indicate the dependency of the partitioned slip rate on the boundary conditions and confirm the existence of interaction among faults. Also, partitioned slip rates show that the Chalderan, Guilato-Siahcheshmeh-Khoy, Nakhchivan, North Tabriz and Pambak-Sevan-Sunik faults are right-lateral strike slip in all cases. Also, the slip rate in these faults is almost symmetric and reaches its maximum value around the center of the faults. We show that the maximum value of slip rate in the fault plane is reduced by partitioning, which it will be definitely closer to reality. According to the gridding for slip rate partitioning in the fault system, the highest value of slip rate is always related to the North Tabriz Fault.
Previous studies show that the geological slip rate estimates are lower than the present-day GPS-derived slip-rates along the North Tabriz fault. We show that slip rate partitioning solves this discrepancy by considering the mechanical interaction among faults. Our partitioned slip rates for North Tabriz Fault are lower than geodetic rates and are more consistent with geological rates. Finally, we present a model that fits best with the geological constraints.
The proximity of the partitioned slip rate to the paleo-seismic values indicates the closeness of the partitioning results to reality with the Boundary Elements Method, compared to other analytical and numerical methods. This research may open new research direction to handle the differene between geologic and geodetic slip rates values in the Iranian Plateau.
The boundary elements method is both faster and more accurate for modeling compared to the finite element method used by Khodaverdian et al. (2015). Considering the effect of topography and sphericity of Earth, using the Galerkin boundary element method developed by Thompson (2019) is proposed to get more realistic results. The coefficients matrix in the of Boundary Elements Method is fully populated and in high dimensions it takes a lot of time to solve the resulting system of equations. Sparsing of the coefficient matrix using wavelet transforms is suggested (Ebrahimnejad et al., 2010) in this study. The use of iterative computational methods along with parallel processing will also reduce the computational time (Thompson and Meade, 2019).

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References

راست‌بود، ا. و وثوقی، ب. (1391). توزیع آهنگ لغزش در سامانه گسل‌های فعال منطقه برخورد مایل صفحه‌های زمین‌ساختی عربستان و اوراسیا براساس روش المان‌های مرزی. فصلنامه علمی علوم زمین، 22(85)، 15-26.
راست‌بود، ا.؛ وثوقی، ب. و طباطبائی، ه. (1392). افراز آهنگ لغزش بین گسل‌های فعال بخش جنوبی البرز مرکزی با وارد کردن برهمکنش مکانیکی بین گسل‌ها. مجله ژئوفیزیک ایران، 7(2)، 78-95.
راست‌بود، ا. (1401). افراز نرخ لغزش در گسل شمال تبریز با استفاده از مشاهدات دائم و دوره‌ای GPS، مجله ژئوفیزیک ایران، 16(1)، 83-102.
راست‌بود، ا. (1402). تحلیل تغییر شکل قاره‌ای زمان حاضر در محدوده فلات ایران با استفاده از تانسور کرنش مستخرج از مشاهدات دائم و دوره‌ای GPS، مجله فیزیک زمین و فضا، 49(1)، 97-117.
شیخ‌الاسلامی، م. ر.؛ جوادی، ح. ر.؛ سرشار، م. ا.؛ آقاحسینی، ا.؛ کوهپیما، م. و دانشمند، ب. و. (1393) دانشنامه گسل‌های ایران، ناشر: سازمان زمین‌شناسی و اکتشافات معدنی کشور، نشر رهی.
Allmendinger, R. W., Reilinger, R., & Loveless, J. (2007). Strain and rotation rate from GPS in Tibet, Anatolia, and the Altiplano. Tectonics, 26, TC3013, doi:10.1029/2006TC002030.
Armijo, R., Flerit, F., King, G., & Meyer, B., (2004). Linear elastic fracture mechanics explains the past and present evolution of the Aegean, 2003. Earth and Planetary Science Letters, 217, 85-95.
Bilham, R. G., & King, G. C. P. (1989). The morphology of strike-slip faults: Examples from the San Andreas fault, California. J. Geophys. Res., 94, 10204-10216.
Bilham, R., & Bodin, P. (1992). Fault zone connectivity: Slip rates on faults in the San Francisco Bay area. Science, 258, 281-284.
Brunet, M. F., Korotaev, M., V., Ershov, A. V., & Nikishin, A. M. (2003). The south caspian basin: a review of its evolution from subsidence modelling. Sedimentary Geology, 156, 119-148.
Cardozo, N., & Allmendinger, R. W. A. (2009). SSPX: A program to compute strain from displacement/velocity data. Comput Geosci-Uk, 35(6), 1343–1357.
Copley, A., & Jackson, J. (2006). Active tectonics of the Turkish-Iranian Plateau. Tectonics, 25(6). 1-19.
Crouch, S.L., & Starfield, A.M. (1990). Boundary Element Methods in Solid Mechanics with Applications in Rock Mechanics and Geological Engineering. Unwin Hyman, London.
Djamour, Y., Vernant, P., Nankali, H. R., & Tavakoli, F. (2011). Nw Iran-Eastern Turkey present-day kinematics: Results from the Iranian permanent GPS network. Earth and Planetary Science Letters, 307(1–2), 27-34.
Ghods A., Shabanian E., Bergman E., Faridi M., Donner S., Mortezanejad G., & Aziz-Zanjani, A., (2015). The Varzaghan–Ahar, Iran, Earthquake Doublet (Mw 6.4, 6.2): implications for the geodynamics of northwest Iran. Geophys. J. Int., 203, 522–540.
Ebrahimnejad, L., Attarnejad R., & Ebrahimnejad H. (2010). Applying wavelets to improve the boundary element method for elasticity problems. Engineering Analysis with Boundary Elements, 34, 810–818.
Ellis, M. E., & King, G. C. P. (1991). Structural control of flank volcanism in continental rifts. Science, 254, 839-842.
Flerit, F., Armijo, R., King, G. C. P., Meyer, B., & Barka A., (2003). Slip partitioning in the Sea of Marmara Pull-Apart determined from GPS velocity vectors. Geophys. J. Int., 154, 1-7.
Gomberg, J. (1991). Seismicity and shear strain in the southern Great Basin of Nevada and California. J. Geophys. Res., 96, 16383-16400.
Gomberg, J. (1992). Tectonic deformation in the New Madrid seismic zone: Inferences from boundary-elementmodeling. Seismol. Res. Lett., 63(3), 407-425.
Gomberg, J., & Ellis, M. (1994). Topography and tectonics of the central New Madrid seismic zone: Results of numerical experiments using a three-dimensional boundary-element program. Journal of Geophysical Research, 99(B10), 20299-20310.
Gomberg, J., & Ellis, M. (1993). 3D-DEF: A user's manual, U.S. Geol. Surv. Open File Rep., 93-547, 22 pp.
GSI (Geological Survey of Iran), 2014. Seismic hazard map preparation (NE and NW regions), Tehran, Iran.
Hackman, M. C., King, G. C. P., & Bilham, R. (1990). The mechanics of the south Iceland seismic zone. J. Geophys. Res., 95, 17339-17352.
Haines, A. J. (1982). Calculating velocity fields across plate boundaries from observed shear rates. Geophys. J. R. astr. Soc., 68, 203-209.
Haines, A. J., & Holt, W. E. (1993). A procedure for obtaining the complete horizontal motions within zones of distributed deformation from the inversion of strain rate data. Journal of Geophysical Research: Solid Earth, 98(B7), 12057-12082, doi:10.1029/93jb00892.
Haji-Aghajany, S., Voosoghi, B., & Yazdian, A. (2017). Estimation of North Tabriz Fault parameters using neural networks and 3D tropospherically corrected surface displacement field. Geomatics, Natural Hazards Risk, 8(2), 918-932. https://doi.org/10.1080/19475705.2017.1289248.
Haji-Aghajany, S., Voosoghi, B., & Yazdian, A. (2019). Estimating the slip rate on the North Tabriz Fault (Iran) from InSAR measurements with tropospheric correction using 3D ray tracing technique. Advances in Space Research, 64, 2199–2208.
Hempton, M. R. (1987). Constraints on Arabian plate motion and extensional history of the Red Sea. Tectonics, 6(6), 687–705, doi:10.1029/ TC006i006p00687.
Hessami, K., Pantosti, D., Tabassi, H., Shabanian, E., Abbasssi, M. R., Feghhi, K., & Solaymani, S. (2003a), Paleoearthquakes and slip rates of the North Tabriz Fault, NW Iran: preliminary results. Annals of Geophysics, 46(5), 903-915.
Hessami, K., Jamali, F., & Tabassi, H. (2003b). Major Active Faults of Iran (map), Ministry of Science, Research and Technology, International Institute of Earthquake Engineering and Seismology.
Hossein-Khan-Nazer, N. (1999). Geomorphological map of Sardrud: Geological Survey of Iran, Report sheet 5266 III, series K753.
Jackson, J. (1992). Partitioning of Strike-Slip and Convergent Motion between Eurasia and Arabia in Eastern Turkey and the Caucasus. J. Geophys. Res., 97(B9), 12471-12479.
Jackson, J. A., Haines, J., & Holt, W. (1995). The accommodation of Arabia-Eurasia plate convergence in Iran. J. Geophys. Res., 100, 15205-15219.
Karakhanian, A. S., Trifonov, V. G., Philip, H., Avagyan, A., Hessami, K., Jamali, F., Bayraktutan, M. S., Bagdassarian, H., Arakelian, S., Davtian, V., & Adilkhanyan, A. (2004). Active faulting and natural hazards in Armenia, eastern Turkey and northwestern Iran. Tectonophysics, 380(3), 189–219.
Karimzadeh, S., Cakir, Z., Osmanoglu, B., Schmalzle, G., Miyajima, M., Amiraslanzadeh, R., & Djamour, Y. (2013). Interseismic strain accumulation across the North Tabriz Fault (NW Iran) deduced from InSAR time series. Journal of Geodynamics, 66, 53–58.
Khodaverdian, A., Zafarani, H., & Rahimian, M. (2015). Long term fault slip rates, distributed deformation rates and forecast of seismicity in the Iranian Plateau. Tectonics, 34(10), 2190–2220, https://doi.org/10.1002/2014TC003796.
Khodaverdian, A., Zafarani, H., & Rahimian, M. (2016). Using a physics-based earthquake simulator to evaluate seismic hazard in NW Iran. Geophysical Journal International, 206(1), 379–394, https://doi.org/10.1093/gji/ggw157.
Khorrami F., Vernant P., Masson F., Nilfouroushan F., Mousavi Z., Nankali H., Saadat S. A., Walpersdorf A., Hosseini S., Tavakoli P., Aghamohammadi A., & Alijanzade M. (2019). An up-to-date crustal deformation map of Iran using integrated campaign-mode and permanent GPS velocities. Geophys. J. Int., 217, 832–843.
King, G. C. P., & Ellis, M. (1990). The origin of large local uplift in extensional regions. Nature, 348, 689-692.
King, G. C. P., Sturdy, D., & Whitney, J. (1993). The landscape geometry and active tectonics of northwest Greece. Geol. Soc. Am. Bull., 105, 137-161.
Kostrov, B. V. (1974). Seismic moment and energy of earthquakes, and seismic flow of rock. Izv. Akad. Sci. USSR, Phys. Solid Earth, 1, 23-44.
Masson, F., Chéry, J., Hatzfeld, D., Martinod, J., Vernant, P., Tavakoli, F., & Ghafory-Ashtiani, M. (2005). Seismic Versus Aseismic Deformation in Iran Inferred from Earthquakes and Geodetic Data. Geophysical Journal International, 160(1), 217-226.
Ommi, S. & Zafarani, H. (2016). Analyses of seismicity parameters of the August 11th, 2012, Ahar-Varzaghan earthquakes in north-western Iran. Scient. Iranica, A, 23, 111.
Masson, F., Djamour, Y., Van-Gorp, S., Chéry, J., Tatar, M., Tavakoli, F., Nankali, H., & Vernant, P. (2006). Extension in Nw Iran driven by the motion of the South Caspian Basin. Earth and Planetary Science Letters, 252(1–2), 180-188.
McClusky, S., Reilinger, R., Mahmoud, S., Ben Sari, D., & Tealeb, A., (2003). GPS constraints on Africa (Nubia) and Arabia plate motions. Geophysical Journal International, 155(1), 126-138.
Okada, Y. (1992). Internal deformation due to shear and tensile faults in a half-space. Bulletin of the Seismological Society of America, 82(2), 1018-1040.
Okada, Y. (1985). Surface deformation due to shear and tensile faults in a half-space. Bulletin of the Seismological Society of America, 75(4), 1135-1154.
Pedrami, M. (1987). Quaternary stratigraphy of Iran. Geologyical Survey of Iran, Internal Report, Serial No. 551.79 (55).
Priestley, K., Baker, C., & Jackson, J. (1994). Implications of Earthquake Focal Mechanism Data for the Active Tectonics of the South Caspian Basin and Surrounding Regions. Geophysical Journal International, 118(1), 111-141.
Reilinger, R., McClusky, S., Vernant, P., Lawrence, S., Ergintav, S., Cakmak, R., Ozener, H., Kadirov, F., Guliev, I., Stepanyan, R., Nadariya, M., Hahubia, G., Mahmoud, S., Sakr, K., ArRajehi, A., Paradissis, D., Al-Aydrus, A., Prilepin, M., Guseva, T., Evren, E., Dmitrotsa, A., Filikov, S.V., Gomez, F., Al-Ghazzi, R., & Karam, G. (2006). Gps Constraints on Continental Deformation in the Africa-Arabia-Eurasia Continental Collision Zone and Implications for the Dynamics of Plate Interactions. J. Geophys. Res., 111(B5), B05411.
Rizza, M., Vernant, J., Ritz, F., Peyret, M., Nankali, H., Nazari, H., Djamour, Y., Salamati, R., Tavakoli, F., Chery, J., Mahan, S., & Masson, F. (2013). Morphotectonic and geodetic evidence for a constant slip-rate over the last 45 kyr along the Tabriz Fault (Iran). Geophysical Journal International, 199(1), 25–37.
Solaymani Azad, S., Philip, H., Dominguez, S., Hessami, K., Shahpasandzadeh, M., Foroutan, M., Tabassi, H., & Lamothe, M. (2015). Paleoseismological and morphological evidence of slip rate variations along the North Tabriz fault (NW Iran). Tectonophysics, 640-641, 20-38.
Sutradhar, A., Paulino, G. H., & Gray, L. J. (2008). Symmetric Galerkin Boundary Element Method, Springer.
Thompson, T. B. (2019). Geometrically Accurate Earthquake Modeling. Doctoral dissertation, Harvard University, Graduate School of Arts & Sciences.
Thompson, T. B., & Meade B. J. (2019). Boundary element methods for earthquake modeling with realistic 3D geometries, Geochemistry, Geophysics, Geosystems, doi:10.31223/dsf.io/xzhuk.
Vernant, P., Nilforoushan, F., Hatzfeld, D., Abassi, M. R., Vigny, C., Masson, F., Nankali, H., Martinod, J., Ashtiani, A., Bayer, R., Tavakoli, F., & Chery, J. (2004). Present-day crustal deformation and plate kinematics in the Middle East constrained by GPS measurements in Iran and northern Oman. Geophysical Journal International, 157, 381-398.
Zanjani, A.A., Ghods, A., Sobouti, F., Bergman, E., Mortezanejad, G., Priestley, K., Madanipour, S., & Rezaeian, M. (2013). Seismicity in the western coast of the South Caspian Basin and the Talesh Mountains, Geophys. J. Int., 195, 799814.
Zafarani, H., Ghafoori, S.M.M., Adlparvar, M.R., Rajaeian, P., & Hasankhani, A. (2015). Application of time-and magnitude-predictable model for long-term earthquake prediction in Iran. Nat. Hazards, 78, 155178.
Journal of the Earth and Space Physics
Volume 49, Issue 2
online publication date: 30 Aug 2023
August 2023
Pages 313-331

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