Assessing seismic hazards of blind thrusts by surface deformation: Kheyrabad anticline, Eastern Iran


Assistant Professor, Department of Mining Engineering, Faculty of Mining Engineering, Civil and Chemistry, Birjand University of Technology


In this research, we investigate the seismic hazard associated with the Kheyrabad blind thrust fault at the north of Birjand, Eastern Iran. Field measurements from a structural transect through the Kheyrabad anticline indicate fault-propagation folding above a 38° northeastward-dipping blind thrust fault which probably reaches into a horizontal detachment at a depth of ~500 meters. In this research, in order to evaluate the seismic risk of Khayrabad blind fault have been investigated, parameters such as average slip rate, maximum earthquake (Mmax) and its recurrence. Obtaining estimates of the slip-rate on the blind fault, and of the rate of crustal shortening are difficult, but we assume that transport of material on the horizontal decollement at depth is balanced by extrusion of material at the surface, we can produce approximate measurements of slip-rate and shortening by using area balancing. In this method, the rates of fault slip, horizontal shortening, and uplift have been estimated as 0.75, 0.59, and 0.46 mm/yr, respectively. Using the regression equation between earthquake magnitude and rupture area, magnitude of the maximum earthquake is estimated at 4.7. Also, using the empirical relationships between magnitude, coseismic displacement and slip rate, the recurrence of this earthquake is predicted to be 577 years. According to the obtained slip rate (0.75 mm/yr), the activity grade of Khairabad blind fault is considered moderate.


Main Subjects

Aki, K., 1966. Generation and propagation of G-waves from the Niigata earthquake of June 16, 1964. Part 2. Estimation of earthquake moment, released energy, and stress–strain drop from the G-wave spectrum. Bulletin of earthquake Research Institute, Tokyo University 44, 73–88.
Alimi, M.A., 2017. Quaternary deformation associated with blind thrust faulting in Kheyrabad anticline, north Brigand. 5th Tectonic and Structural geology of Iran congress.
Berberian, M., 1979. Earthquake faulting and bedding thrust associated with the Tabas-e-Golshan (Iran) earthquake of September 16, 1978. Bulletin of the Seismological Society of America 69, 1861–1887.
Berberian, M., Jackson, J.A., Qorashi, M., Talebian, M., Khatib, M.M., Priestley, K., 2000. The 1994 Sefidabeh earthquakes in eastern Iran: Blind thrusting and bedding-plane slip on a growing anticline, and active tectonics of the Sistan suture zone. Geophysical Journal International 142, 283–299.
Copley, A., and Reynolds, K., 2014. Imaging topographic growth by long-lived postseismic after slip at Sefidabeh, east Iran. Tectonics 33, TC003462.
Copley, A., 2014. Postseismic after slip 30 years after the 1978 Tabas-e-Golshan (Iran) earthquake. observations and implications for the geological evolution of thrust belts. Geophysical Journal International 197(2), 665-679.
 Davis, G.H., Reynolds, S.J., Kluth, Ch.F., 2012. Structural geology of rocks and regions. Wiley and Sons press, p. 861.
Eftekhar Nezhad, J., Ohanian, T., Tatevosian, S., Manouchehri, M., Afaghi, A., Hosseini, Z., Qomashi, A., Afsharian Zadeh, A., Etemadi, N., 1986. Geological Map of Birjand, Scale: 1:100,000, Geological Survey of Iran, Tehran.
Engdahl, E.R., Jackson, J.A., Myers, S.C., Bergman, E.A., Priestley, K., 2006. Relocation and assessment of seismicity in the Iran region. Geophysical Journal International 167, 761–778.
Engdahl, E.R., van der Hilst, R., Buland, R., 1998. Global teleseismic earthquake relocation with improved travel times and procedures for depth determination. Bulletin of the Seismological Society of America 88, 722–743.
Groshong, R.H., 2006. 3-D Structural Geology. Springer Publications, P. 400.
Hollingsworth, J., Fattahi, M., Walker, R.T, Talebian, M., Bahroudi, A., Bolourchi, M., Jackson, J.A., Copley, A., 2010. Oroclinal bending, distributed thrust and strike-slip faulting, and the accommodation of Arabia-Eurasia convergence in NE Iran since the Oligocene. Geophysical Journal International 181, 1214–1246.
ISC. Iranian Seismological Center.
Keller, E.A., Pinter, N., 2002. Active tectonics, Earthquakes, Uplift and Landscape. Prentice Hall, P. 362.
King, G., Soufleris, C., Berberian, M., 1981. The source parameters, surface deformation and tectonic setting of three recent earthquakes. Thessaloniki (Greece); Tabas-e-Golshan (Iran); and Carlisle (U.K.). Disasters 5, 36–46.
Lin, J., Stein, R.S., 1989. Coseismic folding, earthquake recurrence and the 1987 source mechanism at Whittier Narrows, Los Angeles Basin, California. Geophysical Journal International 94, 9614-9632.
Lin, J., Stein, R.S., 2004. Stress triggering in thrust and subduction earthquakes and stress interaction between the southern San Andreas and nearby thrust and strike-slip faults. Journal of Geophysical Research 109, B02303.
McCalpin, J.P., Carver, G.A, 1996. Paleoseismology of Compressional Tectonic Environments. International Geophysics 62, 183-270,
NEIC. National Earthquake Information Center. United State Geological Survey Stop 967, National Earthquake Information Center, DFC, Denver, CO 80225-0046, USA.
Parsons, B., Wright, T., Rowe, P., Andrews, J., Jackson, J., Walker, R., Khatib, M., Talebian, M., Bergman, E., Engdahl, E.R., 2006. The 1994 Sefidabeh (eastern Iran) earthquakes revisited: new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault. Geophysical Journal International 164, 202–217.
Rivero, C., Shaw, J.H., Mueller, K., 2000. Oceanside and Thirty-mile Bank blind thrusts: Implications for earthquake hazards in coastal southern California. Geology 28, 891–894.;2
Shaw, J.H., Suppe, J., 1996. Earthquake hazards of active blind-thrust faults under the central Los Angeles Basin, California. Journal of Geophysical research 101, 8623–8642.
Stein, R.S., Yeats, R.S., 1989. Hidden earthquakes. Scientific American 260, 48–57.
Walker, R., Khatib, M.M., 2006. Active faulting in the Birjand region of NE Iran, Tectonics 25, TC4016,
Walker, R., Jackson, J., Baker, C., 2003. Surface expression of thrust faulting in eastern Iran: source parameters and surface deformation of the 1978 Tabas and 1968 Ferdows earthquake sequences. Geophysical Journal International 152, 749–765.
Walker, R., Jackson, J., Baker, C., 2004. Active faulting and seismicity of the Dasht-e Bayaz region, eastern Iran. Geophysical Journal International 157, 265–285.
Walker, R.T., Khatib, M.M., Bahroudi, A., Schnabel, C., Rode´s, A., Fattahi, M., Talebian, M., Bergman, E., 2015. Co-seismic, Geomorphic, and Geologic fold growth associated with the 1978 Tabas earthquake fault in eastern Iran. Geomorphology 237, 98-118.
Wells, D.L., Coppersmith, K.J., 1994. Empirical relationships among magnitude, rupture length, rupture area, and surface displacement. Bulletin of the Seismological Society of America 84, 974–1002.