Splay Faults in the Makran Subduction Zone and Changes of their Transferred Coulomb Stress


1 M.Sc. Geophysics, Department of engineering, Islamic Azad university Marivan branch, Marivan, Iran

2 Ph.D. Student, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran

3 Assistant Professor, Department of Seismology, International Institute of Earthquake Engineering and seismology(IIEES), Tehran, Iran


The Makran subduction zone in northeast and the Sumatra subduction zone (Sunda) in the west have been known as tsunamigenic zones of the Indian Ocean. The 990 km long Makran subduction zone is located offshore of Iran, Pakistan and Oman. Similar to many subduction zones all over the world, the Makran accretionary prism is associated with an imbricate of thrust faults across the zone, which may rupture due to great earthquakes. Based on some studies, it has been suggested that the presence of young marine terraces along parts of the western Makran, Jask, and Konarak, providing a strong evidence for the occurrence of great thrust earthquakes in the western Makran. Besides, this region might have experienced a strong earthquake in 1483 (Mw=7.2). This study uses 2D seismic reflection data to map the splay faults in the western Makran subduction zone. The result of this interpretation has been presented on map showing the major splay and normal faults, in the south and north, respectively. Furthermore, Coulomb stress changes is calculated along the splay faults, following a hypothetical earthquake (Mw=7.2) on the megathrust. The amount of slip that transfers from the plate boundary onto the splay faults during large subduction earthquake and the pattern of slip partitioning between them are calculated. The results show that the slip on Megathrust increases stress in some parts of surrounding areas. Some splay faults are located in these areas that can be loaded in shallow depth and are likely the sources of aftershocks. Since the slip on splay faults has a key significance in generating tsunami, their analysis is an important issue in tsunami risk assessment. It is strongly suggested that the result of this study is used as an input parameter for a comprehensive tsunami hazard modeling in the Makran region.


Main Subjects

Ambraseys, N. and Melville, C., 1982, A History of Persian Earthquakes. Cambridge University Press, New York.
Baba, T., Cummins, Ph. R., Hori, T., and Kaneda, Y., 2006, High precision slip distribution of the 1944 Tonankai earthquake inferred from tsunami waveforms: Possible slip on a splay fault, Tectonophysics, 426, 119–134, doi:10.1016/j.tecto.2006.02.015.
Byrne, D. E., Sykes, L. R., and Davis, D. M., 1992, Great thrust earthquakes and a seismic slip along the plate boundary of the Makran subduction zone. J. Geophys. Res., 97, 449–478.
Cummins, Ph. R. and Kaneda, Y., 2000, Possible splay fault slip during the 1946 Nankai earthquake. Geophysical Research Letters, 27, 17, 2725–2728.
Cattin, R., Chamot-Rooke, N., Pubellier, M., Rabaute, A., Delescluse, M., Vigny, C., Fleitout, L. and Dubernet, P., 2009, Stress change and effective friction coefficient along the Sumatra-Andaman-Sagaing fault system after the 26 December 2004 (Mw = 9.2) and the 28 March 2005 (Mw = 8.7) earthquakes, AGU and the Geochemical Society, 10(3), Q03011, doi:10.1029/2008GC002167 ISSN: 1525-2027.
De Mets, C., Gordon, R. G., Argus, D. F. and Stein, S., 1990, Current plate motions. Geophys. J. Int., 101, 425–478.
Farhoudi, G. and Karig, D. E., 1977, The Makran of Iran and Pakistan as an Active Arc System. Abstr., EOS Trans., Am. Geophys. Union., 58, 446.
Grando, G. and McClay, K., 2007, Morphotectonics domains and structural styles in the Makran accretionary prism, offshore Iran. Sedimentary Geology, 196, 157–179.
Hanks, T. C. and Kanamori, H., 1979, A moment magnitude scale, Journal of Geophysical Research, 84, 2348-2350.
Kame, N., Rice, J. R. and Dmowska, R., 2003, Effects of prestress state and rupture velocity on the energy release in great earthquakes. Journal of Geophysical Research, Journal of Geophysical Research, 84, 2303–2314.
King, G. C. P., Stein, R. S. and Lin, J., 1994, Static stress changes and the triggering earthquakes, Bull. Seismol. Soc. Am., 84(3), 935- 953.
Lin, J. and 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, Vol. B02303, doi:10.1029/2003JB002607.
Mokhtari, M., Abdollahie Fard, I. and Khaled Hessami, H., 2008, Structural elements of the Makran region, Oman sea and their potential relevance to tsunamigenisis. Natural Hazards, 47, 185–199.
Mouyen, M., Cattin, R. and Masson, F., 2010, Seismic cycle stress change in western Taiwan over the last 270 years. Geophysical Research Letters, 37(3).
Page, W. D., Alt, J. N., Cluff, L. S. and Plafker, G., 1979, Evidence for the recurrence of large magnitude earthquakes along the Makran coast of Iran and Pakistan. Tectonophysics, 52, 533–547.
Parsons, T., Stein, R. S., Simpson, R. W. and Reasenberg, P. A., 1999, Stress sensitivity of fault seismicity: A comparison between limited-offset oblique and major strike-slip faults, J. Geophys. Res., 104, 20,183–20,202.
Ryan, H. F. and Scholl, D. W., 1989, The evolution of forearc structures along an oblique convergent margin, central Aleutian Arc. Tectonics, 8, 497–516.
Sykes, L. R. and Menke, W., 2006, Repeat times of large earthquakes: implications for earthquake mechanics, Bulletin of the Seismological Society of America, 96, 5, 1569–1596.
Toda, S. and Stein, R. S., 2003, Toggling of seismicity by the 1997 Kagoshima earthquake couplet: A demonstration of time-dependent stress transfer, J. Geophys. Res., 108(B12), 2567, doi:10.1029/ 2003JB002527.
Vernant, P., Nilforoushan, F., Hatzfeld, D., Abbassi, M. R., Vigny, C., Masson, F., Nankali, H., Martinod, J., Ashtiani, A., Bayer, R., Tavakoli, F. and Ch´ery, J., 2004, Contemporary crustal deformation and plate kinematics in the Middle East constrained by GPS measurements in Iran and Northern Oman, Geophys. J. Int., 157, 381–398.  
Wells, D. L. and Coppersmith, K. J., 1994, New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement. Bulletin of the Seismological Society of America, 84.
Zarifi Z., 2006, Unusual subduction zones: case studies in Colombia and Iran, Unpublished Ph.D. Thesis., University of Bergen, Norway.