ALBERT

Description: Tsunami waves were observed along the Bulgarian Black Sea coastline on May 7, 2007. The maximum rise and fall of the sea-level were 1.2 versus 2.0 m, respectively, with wave oscillations between 4-8 minutes. At first submarine landsliding and then later on atmospheric disturbance were suggested as the cause of the tsunami. Numerical modeling by Gusev et al. (2019), assuming a landslide displacing 30 to 60 million m3 material on the slope with a thickness range of over 20-40 m, could produce similar characteristics of the recorded tsunami. In the recent model the landslide initiated on the shelf at a water depth of 100 m with a runout of about 20 km into 1000 m water depth. Subsequent and recent numerical modeling suggested that the failure may have initiated on the slope, anywhere between 200 to 1500 m seafloor depth. The runout of the transported sediments in these latest model was at 1850 m water depth. Just a few years after the tsunami, OMV and its joint venture partners, TOTAL and Repsol, acquired modern deepwater data sets in the same area where the submarine landsliding was assumed to occur. These data sets included multi-beam swath bathymetry area and acquisition of a 3D reflection seismic data. These data sets offer a possibility to establish the presence of speculative submarine landslide responsible for the tsunami, with its geometry and nature. Our results provide direct evidence for the occurrence of large, non-seismic, catastrophic sediment failures along the Bulgarian coast. In this study we illustrate Quaternary submarine landslides on 3D seismic reflection data immediately below than the one responsible for the 2007 event, besides we also briefly point out the potential interpretation pitfall related to sediment waves and mass transport complexes.