15:30 〜 15:45
[HDS06-01] Landslide tsunami hazards in Indonesia
キーワード：Tsunami, Landslide, Earthquake , Indonesia
The recent global tsunami generated by the January 2022 Tonga volcanic tsunami once again renewed attention to non-seismic tsunamis generated by volcanoes and landslides (Heidarzadeh et al., 2022: https://doi.org/10.1016/j.oceaneng.2022.112165). Such tsunamis have been responsible for a number of destructive events in Indonesia including the 1883 tsunami following the Krakatau eruption which costed at least 36,000 lives and the recent two devastating events in 2018: the Palu (Sulawesi) (more than 4,000 deaths) and Anak Krakatau (more than 450 deaths) tsunamis. This clearly shows the importance of more research works on understanding the generation mechanisms and potential for tsunamis from landslides and volcanoes in Indonesia. Here, we study three recent tsunamis in Indonesia which are generated or contributed by landslides, two of which occurred following an earthquake while the other one occurred following a volcanic eruption. All of these three events have a landslide component in their sources. The events are: (1) the June 2021 Seram Island tsunami which was originated by an earthquake and was contributed by a submarine landslide. (2) The December 2018 Palu tsunami which was also originated by an earthquake followed by a submarine landslide. And (3) The December 2018 Anak Krakatau tsunami caused a subaerial landslide following a massive volcanic eruption.
A tsunami was observed on 16th June 2021 in Seram Island following a normal-faulting Mw 5.9 earthquake. The tsunami amplitude was approximately 50 cm at Tehoru tide gauge whereas two other stations showed amplitudes of less than 4 cm. Such a relatively large tsunami (50 cm) is unexpected from an Mw 5.9 earthquake. We hypothesize that a secondary source (i.e., a landslide) was involved. We applied tsunami modelling and source analysis to examine this hypothesis. Tsunami simulations confirmed that the earthquake could only have contributed to a few centimeters of the tsunami and thus cannot reproduce the 50 cm waves. However, we could reproduce the tsunami observations using a landslide source. For more information see here: https://doi.org/10.1785/0120210274.
Regarding the September 2018 Palu tsunami, it is now commonly accepted that a submarine landslide should have most likely contributed to the tsunami generation in addition to the earthquake. However, the nature of the landslide whether submarine or subaerial, and the contribution of the two sources are not clear. We propose a novel dual landslide-earthquake source that explains most of the observation of the 2018 Palu event. Our dual model comprises the USGS earthquake model (length = 264 km, width = 37 km, slip = 0 – 8.5 m) combined with a submarine landslide with a length of 1.0 km, a width of 2.0 km, and a thickness of 80.0 m. For more information see here: https://doi.org/10.1080/21664250.2022.2122293.
For the December 2018 Anak Krakatau tsunami, we present the results of our field surveys. We surveyed 29 locations along southern coast of the Sunda Strait along the coastline from Ciwandan to Ujung Kulon National Park, and measured tsunami runups from 0.9 m to 5.2 m, tsunami heights from 1.4 to 6.3 m, and inundation distances from 18 to 212 m. For more information, see here: https://doi.org/10.1007/s00024-020-02587-w.
This research is funded by The Royal Society (UK), grant number CHL/R1/180173.
A tsunami was observed on 16th June 2021 in Seram Island following a normal-faulting Mw 5.9 earthquake. The tsunami amplitude was approximately 50 cm at Tehoru tide gauge whereas two other stations showed amplitudes of less than 4 cm. Such a relatively large tsunami (50 cm) is unexpected from an Mw 5.9 earthquake. We hypothesize that a secondary source (i.e., a landslide) was involved. We applied tsunami modelling and source analysis to examine this hypothesis. Tsunami simulations confirmed that the earthquake could only have contributed to a few centimeters of the tsunami and thus cannot reproduce the 50 cm waves. However, we could reproduce the tsunami observations using a landslide source. For more information see here: https://doi.org/10.1785/0120210274.
Regarding the September 2018 Palu tsunami, it is now commonly accepted that a submarine landslide should have most likely contributed to the tsunami generation in addition to the earthquake. However, the nature of the landslide whether submarine or subaerial, and the contribution of the two sources are not clear. We propose a novel dual landslide-earthquake source that explains most of the observation of the 2018 Palu event. Our dual model comprises the USGS earthquake model (length = 264 km, width = 37 km, slip = 0 – 8.5 m) combined with a submarine landslide with a length of 1.0 km, a width of 2.0 km, and a thickness of 80.0 m. For more information see here: https://doi.org/10.1080/21664250.2022.2122293.
For the December 2018 Anak Krakatau tsunami, we present the results of our field surveys. We surveyed 29 locations along southern coast of the Sunda Strait along the coastline from Ciwandan to Ujung Kulon National Park, and measured tsunami runups from 0.9 m to 5.2 m, tsunami heights from 1.4 to 6.3 m, and inundation distances from 18 to 212 m. For more information, see here: https://doi.org/10.1007/s00024-020-02587-w.
This research is funded by The Royal Society (UK), grant number CHL/R1/180173.