Submarine landslides at the eastern Sunda margin: observations and tsunami impact assessment

Abstract

Our analysis of new bathymetric data reveals six submarine landslides at the eastern Sunda margin between central Java and Sumba Island, Indonesia. Their volumes range between 1 km³ in the Java fore-arc basin up to 20 km³ at the trench off Sumba and Sumbawa. We estimate the potential hazard of each event by modeling the corresponding tsunami and its run-up on nearby coasts. Four slides are situated remarkably close to the epicenter of the 1977 tsunamigenic Sumba M w =8.3 earthquake. However, comparison of documented tsunami run-up heights and arrival times with our modeling results neither allows us to confirm nor to decline the hypothesis that the earthquake triggered these submarine landslides.

Landslide tsunami hazard in the Indonesian Sunda Arc

“…The largest slides of our study (sites 9, 11, and 12 with a volume of 15 to 20 km 3 ) were found 150 km southeast of Sumba and 250 km south of Sumbawa (in Brune et al, 2009b, they are denominated C, E, and F, respectively). They generated large tsunamis with maximum run-up heights of nearly 6 m on Sumbawa for slides 9 and 11.…”

“…We studied whether the slope failures generated a tsunami and how much run-up was generated at the shore using numerical tsunami modeling for the events at site 4 (Brune et al, 2009a) and 7 to 12 (Brune et al, 2009b). We thereby applied the nonlinear shallow water code TUNAMI-N2 (Imamura et al, 1997) to calculate wave propagation from the slide to the shore.…”

“…Therefore, we refer to the obtained results as effective "estimated run-up heights". For a detailed description of the applied modeling techniques we refer to Brune et al (2009b).…”

“…For each scenario an initial wave form was computed in analogy to Watts et al (2005) (see also Brune et al, 2009b). The wave shape is composed of a wave crest and a trough in positive and negative slide direction, respectively.…”

Morphology of the Andaman outer shelf and upper slope of the Thai exclusive economic zone

“…Intrinsic amplitude accuracy regarding the equation is ±5.3%. The results show that the observed landslide would have generated a tsunami wave of about 4450 m wave length and with a maximum wave height of about 0.12 m. These initial wave characteristics could be input criteria for tsunami propagation models (Synolakis et al, 2002;Brune et al, 2009) in order to calculate wave propagation and potential onshore run-up. However, the small initial wave height already indicates that the observed submarine landslide could not generate a devastating tsunami on the coast.…”