Tsunami and storm sediments in Oman: Characterizing extreme wave deposits using terrestrial laser scanning

摘要

Accurate determination of geometric parameters is key to a holistic understanding of storm and tsunami deposits and for modeling wave magnitudes responsible for the displacement of large boulders. We present a new approach in acquiring high-resolution geometric data on coastal boulder deposits related to extreme wave events. The reconstruction of boulder movements along coastlines contributes to a better understanding of storm and tsunami dynamics. Critical parameters for both determining their origin of the event, and providing more accurate modeling parameters, include boulder size, shape, weight, age and lithology. We used terrestrial laser scanning (TLS) on two sites with 327 boulders along the Oman coastline in order to prove the method's validity. TLS results in very accurate and detailed three dimensional reconstructions of the boulders and can be used to reconstruct the origin of the boulders based on shape and texture. The method also provides refined size, volume and mass estimates for the boulders. According to the results at least 3 large-scale inundation events were recorded on the northeastern Oman coastline during the late Holocene. Dating results on displaced beach rock boulders suggest severe events around 7540 +/- 120 cal yr. BP, 1175 +/- 115 cal yr. BP and 265 +/- 155 cal yr. BP, which each left a clear and distinctive coastal boulder ridge. The largest displaced boulder has a length of 7.36 m, a calculated mass of 120.5 t, and experienced a vertical uplift of 1.3 m during an inundation event. The results suggest a tsunamigenic origin of the coastal boulder trains, and highlight a potential of strong tsunami events along the Omani coastline.