Tsunami scenario triggered by submarine landslide offshore of northern Sumatra Island and its hazard assessment

Near the northern border of Sumatra, the right-lateral strike-slip Sumatran Fault Zone splits into two branches and extends into the offshore, as revealed by seismic sounding surveys. However, due to its strike-slip faulting characteristics, the Sumatran Fault Zone’s activity is rarely believed to cause tsunami hazards in this region. According to two reprocessed reflection seismic profiles, the extended Sumatran Fault Zone is strongly associated with chaotic facies, indicating that large submarine landslides have been triggered. Coastal steep slopes and new subsurface characteristics of submarine landslide deposits were mapped using recently acquired high-resolution shallow bathymetry data. Slope stability analysis revealed some targets with steep morphology to be close to failure. In an extreme case, an earthquake of Mw 7 or more occurred, and the strong ground shaking triggered a submarine landslide off the northern shore of Sumatra. Based on a simulation of tsunami wave propagation in shallow water, the results of this study indicate a potential tsunami hazard from a submarine landslide triggered by the strike-slip fault system. The landslide tsunami hazard assessment and early warning systems in this study area can be improved on the basis of this proposed scenario.

Probabilistic hazard assessment: Application to geomagnetic activity

Probabilistic Hazard Assessment (PHA) provides an appropriate methodology for assessing space weather hazard and its impact on technology. PHA is widely used in the geosciences to determine the probability of exceedance of critical thresholds, caused by one or more hazard sources. PHA has proved useful where there are limited historical data to estimate the likelihood of specific impacts. PHA has also driven the development of empirical and physical models, or ensembles of models, to replace measured data. Here we aim to highlight the PHA method to the space weather community and provide an example of it could be used. In terms of space weather impact, the critical hazard thresholds might include the Geomagnetically Induced Current in a specific high voltage power transformer neutral, or the local pipe-to-soil potential in a particular metal pipe. We illustrate PHA in the space weather context by applying it to a twelve-year dataset of Earth-directed solar Coronal Mass Ejections (CME), which we relate to the probability that the global three-hourly geomagnetic activity index K p exceeds specific thresholds. We call this a ‘Probabilistic Geomagnetic Hazard Assessment’, or PGHA. This provides a simple but concrete example of the method. We find that the cumulative probability of K p > 6-, > 7-, > 8- and K p = 9o is 0.359, 0.227, 0.090, 0.011, respectively, following observation of an Earth-directed CME, summed over all CME launch speeds and solar source locations. This represents an order of magnitude increase in the a priori probability of exceeding these thresholds, according to the historical K p distribution. For the lower Kp thresholds, the results are distorted somewhat by our exclusion of coronal hole high speed stream effects. The PGHA also reveals useful (for operational forecasters) probabilistic associations between solar source location and subsequent maximum Kp .

Landslide Hazard Assessment and Runout Simulation by Utilizing Remote Sensing, Geophysical, and Geological Techniques

Landslide events in Karakorum ranges are frequent and have already damaged local infrastructures and roads. In the hilly regions, landslide characterization and predicting its deposition pattern are essential for accurate engineering hazard assessment. To this end, numerical simulation models are commonly used tools. However, appropriate model parameters are often not available to predict and generate real landslide scenarios. This work describes the use of multidisciplinary techniques to estimate the model parameters for a slope prone to landslide and simulate the hazard level. The first important parameter, landslide boundary, and dynamics were estimated from temporal satellite images by identifying the areas with prominent deformations using the Interferometric Synthetic Aperture Radar (InSAR) technique. The susceptible subsurface strata volume and the possible landslide initiation depth were determined with the electrical resistivity method. In addition, voxel 3D electrical resistivity models were created to present the depth of the existing rupture and the nature of subsurface strata. The soil mechanical parameters were calculated during field visits and laboratory tests. The parameters adopted from different techniques helped simulate the susceptible landslide volume and initiation depth. These parameters are a critical factor in developing an accurate high-speed landslide model through numerical simulation. The applied methodology is vital to understand the dynamics of a particular slope and perform accurate engineering hazard assessment with numerical simulation. The results are essential to predict the potential deposition areas of the landslide event accurately, minimize the risk level, and take proactive mitigation measures.