Near-field tsunami hazard map Padang, West Sumatra: Utilizing high resolution geospatial data and reseasonable source scenarios

Near-field tsunami propagation both in shallow water environments and bore-like wave propagation on land are conducted in this study to obtain fundamental knowledge on the tsunami hazard potential in the city of Padang, Western Sumatra, Republic of Indonesia. As the region proves a huge seismic moment deficit which has progressively accumulated since the last recorded major earthquakes in 1797 and 1833, this investigation focuses on most reasonable seismic sources and possibly triggered near-shore tsunamis in order to develop upgraded disaster mitigations programs in this densely-populated urban agglomeration located on the western shore of Sumatra Island. Observations from continuous Global Positioning Satellite (cGPS) systems and supplementary coral growth studies confirm a much greater probability of occurrence that a major earthquake and subsequent tsunami are likely to strike the region in the near future. Newly surveyed and processed sets of geodata have been collected and used to progress most plausible rupture scenarios to approximate the extent and magnitudes of a further earthquake. Based upon this novel understanding, the present analysis applies two hydronumerical codes to simulate most probable tsunami run-up and subsequent inundations in the city of Padang in very fine resolution. Run-up heights and flow-depths are determined stemming from these most plausible rupture scenarios. Evaluation of outcome and performance of both numerical tools regarding impacts of surge flow and bore-like wave fronts encountering the coast and inundating the city are thoroughly carried out. Results are discussed not only for further scientific purposes, i.e. benchmark tests, but also to disseminate main findings to responsible authorities in Padang with the objective to distribute the most probable dataset of plausible tsunami inundations as well as to address valuable insights and knowledge for effective counter measures, i.e. evacuation routes and shelter building. Following evacuation simulations based on rational assumptions and simplifications reveal a most alerting result as about 265.000 people are living in the highly exposed potential tsunami inundation area in the city of Padang of which more than 95.000 people will need more than 30 min. to evacuate to safe areas.DFGBMB

Frictional afterslip following the 2005 Nias-Simeulue earthquake, Sumatra

Science, v. 312, n. 5782, p. 1921-1926, 2006. http://dx.doi.org/10.1126/science.1126960International audienceContinuously recording Global Positioning System stations near the 28 March 2005 rupture of the Sunda megathrust [moment magnitude (Mw) 8.7] show that the earthquake triggered aseismic frictional afterslip on the subduction megathrust, with a major fraction of this slip in the up-dip direction from the main rupture. Eleven months after the main shock, afterslip continues at rates several times the average interseismic rate, resulting in deformation equivalent to at least a Mw 8.2 earthquake. In general, along-strike variations in frictional behavior appear to persist over multiple earthquake cycles. Aftershocks cluster along the boundary between the region of coseismic slip and the up-dip creeping zone. We observe that the cumulative number of aftershocks increases linearly with postseismic displacements; this finding suggests that the temporal evolution of aftershocks is governed by afterslip

Extending instrumental sea‐level records using coral microatolls, an example from Southeast Asia

The small number of reliable long-term (i.e., >50 yrs) tide gauges in tropical locations is a major source of uncertainty in modern sea-level change. Coral microatolls record relative sea-level (RSL) change over their lifetimes and have the potential to extend the instrumental record. Here, we examined a 20th and 21st century RSL record from two living coral microatolls from Mapur Island, Indonesia, which produced 16 sea-level index points. We validated and combined the living coral microatoll data with tide gauge data to show RSL at Mapur Island was 0.0 ± 1.6 mm/yr (2σ) from 1915 to 1990 and 1.0 ± 2.1 mm/yr (2σ) from 1990 to 2019. Through the addition of microatoll RSL data we extended the record of modern sea-level change by over 50 years and reduced its uncertainty by ∼50%