Tsunami in Makran Region and Its Effect on the Persian Gulf

Abstract

The Makran Subduction Zone characterizes by the subduction of the oceanic part of the Arabian plate beneath the Eurasian plate. The offshore Makran region located in the Oman Gulf shows relatively low seismicity in comparison with the surrounding regions (Figure 1). In spite of low seismicity, 3 tsunamis in the Makran region has been reported. 2 of them had known seismic source, and the other one has unknown origin. The most recent tsunamigenic event was on November 1945 associated with an earthquake of magnitude 8.1, affecting along the Makran coastlines of Iran, Pakistan, Oman and United Arab Emirates; with the loss of life of around 4000. Since then a long silence poses a potential threat of major tsunamigenic disaster for the coastal region. Makran Subduction Zone is unique region in the world due to its geological and seismological characteristics. High sediment input of 7 km, shallow angle of dip and rate of subduction are interesting and distinctive features of this zone. The Makran subduction zone appears to be divided into at least two segments the west and the east, separated by a sinistral fault known as the Sonne Fault. This has been supported by Kukowski et al., (2000) where they introduce a new boundary coinciding very well with the Sonne strike-slip fault. In contrast to east, the western segment characterizes by absence of inter-plate events. The lack of major earthquakes in the western segment either means the segment has been locked and accumulating strain energy for hundreds of years or it is creeping aseismically. This movement supported by the regional GPS study that indicates a convergence of about 2 cm/year (Bayer et al., 2006). In addition, the existence of Holocene (10,000 years) marine terraces (Page et al., 1979) indicates that this segment is active, although the recurrence period of earthquakes (> 8.0) may be much longer (i.e. thousands of years). In this context, it is important to mention that the western segment of the Makran subduction zone may have experienced a large offshore earthquake in 1483 (Ambraseys and Melville, 1982). Although recent work suggests this may have been a moderate event near the Qeshm Island, Strait of Hormuz in association with the Zagros seismically active region (Musson, 2008). Based on the 2D offshore seismic reflection data the main structural provinces and elements in the Gulf of Oman are (i) the structural elements on the northeastern part of the Arabian Plate and (ii) the Offshore Makran Accretionary Complex Elements. On the northeastern part of the Arabian Plate, five structural provinces and elements being defined: the