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Abstract. We present the GITEWS approach to source modeling for the tsunami early warning in Indonesia. Near-field tsunami implies special requirements to both warning time and details of source characterization. To meet these requirements, we employ geophysical and geological information to predefine a maximum number of rupture parameters. We discretize the tsunamigenic Sunda plate interface into an ordered grid of patches (150×25) and employ the concept of Green's functions for forward and inverse rupture modeling. Rupture Generator, a forward modeling tool, additionally employs different scaling laws and slip shape functions to construct physically reasonable source models using basic seismic information only (magnitude and epicenter location). GITEWS runs a library of semi- and fully-synthetic scenarios to be extensively employed by system testing as well as by warning center personnel teaching and training. Near real-time GPS observations are a very valuable complement to the local tsunami warning system. Their inversion provides quick (within a few minutes on an event) estimation of the earthquake magnitude, rupture position and, in case of sufficient station coverage, details of slip distribution.

Abstract. Despite having been rather seismically quiescent for the last decades, the Makran subduction zone is capable of hosting destructive earthquakes and tsunami. In particular, the well-known thrust event in 1945 (Balochistan earthquake) led to about 4000 casualties. Nowadays, the coastal regions are more densely populated and vulnerable to similar events. Furthermore, some recent publications discuss rare but significantly larger events at the Makran subduction zone as possible scenarios. We analyze the instrumental and historical seismicity at the subduction plate interface and generate various synthetic earthquake catalogs spanning 300 000 years with varying magnitude-frequency relations. For every event in the catalogs we compute estimated tsunami heights and present the resulting tsunami hazard along the coasts of Pakistan, Iran and Oman in the form of probabilistic tsunami hazard curves. We show how the hazard results depend on variation of the Gutenberg–Richter parameters and especially maximum magnitude assumption.

Abstract. Taking the 2011 Tohoku earthquake as an example, we demonstrate the ability of real-time GPS to provide qualified tsunami early warning within minutes. While in earlier studies we demonstrated the power of the so-called GPS shield concept based on synthetic data, we here present a complete processing chain starting from actual GPS raw data and fully simulate the situation as it would be in a warning center. The procedure includes processing of GPS observations with predicted high precision orbits, inversion for slip and computation of the tsunami propagation and coastal warning levels. We show that in case of the Tohoku earthquake, it would be feasible to provide accurate tsunami warning as soon as 3 min after the beginning of the earthquake.

Possibilities of forecasting of a tsunami characteristics for areas with small base of historical tsunami are discussed. The PTHA method (Probabilistic Tsunami Hazard Assessment), which cornerstone the statistical analysis of real and predictive earthquakes which number is rather big, with the subsequent calculation of waves of a Tsunami from possible earthquakes is for this purpose used. This method for assessment of long-term tsunami danger on the Mediterranean coast of Egypt is used. It is shown that the predicted wave heights change along the coast that is caused by heterogeneity of topography of a coastal zone and features of the chart of radiation of a tsunami in the sea. The predicted wave heights for 1000 years change within 0.83.4 m.

Abstract. The Indonesian archipelago is known for the occurrence of catastrophic earthquake-generated tsunamis along the Sunda Arc. The tsunami hazard associated with submarine landslides however has not been fully addressed. In this paper, we compile the known tsunamigenic events where landslide involvement is certain and summarize the properties of published landslides that were identified with geophysical methods. We depict novel mass movements, found in newly available bathymetry, and determine their key parameters. Using numerical modeling, we compute possible tsunami scenarios. Furthermore, we propose a way of identifying landslide tsunamis using an array of few buoys with bottom pressure units.

Abstract. A new tsunami forecasting method for near-field tsunami warning is presented. This method is applied in the German-Indonesian Tsunami Early Warning System, as part of the Indonesian Tsunami Warning Center in Jakarta, Indonesia. The method employs a rigorous approach to minimize uncertainty in the assessment of tsunami hazard in the near-field. Multiple independent sensors are evaluated simultaneously in order to achieve an accurate estimation of coastal arrival times and wave heights within very short time after a submarine earthquake event. The method is validated employing a synthetic (simulated) tsunami event, and in hindcasting the minor tsunami following the Padang 30 September 2009 earthquake.

Abstract. Fostered by and embedded in the general development of information and communications technology (ICT), the evolution of tsunami warning systems (TWS) shows a significant development from seismic-centred to multi-sensor system architectures using additional sensors (e.g. tide gauges and buoys) for the detection of tsunami waves in the ocean. Currently, the beginning implementation of regional tsunami warning infrastructures indicates a new phase in the development of TWS. A new generation of TWS should not only be able to realise multi-sensor monitoring for tsunami detection. Moreover, these systems have to be capable to form a collaborative communication infrastructure of distributed tsunami warning systems in order to implement regional, ocean-wide monitoring and warning strategies. In the context of the development of the German Indonesian Tsunami Early Warning System (GITEWS) and in the EU-funded FP6 project Distant Early Warning System (DEWS), a service platform for both sensor integration and warning dissemination has been newly developed and demonstrated. In particular, standards of the Open Geospatial Consortium (OGC) and the Organization for the Advancement of Structured Information Standards (OASIS) have been successfully incorporated. In the FP7 project Collaborative, Complex and Critical Decision-Support in Evolving Crises (TRIDEC), new developments in ICT (e.g. complex event processing (CEP) and event-driven architecture (EDA)) are used to extend the existing platform to realise a component-based technology framework for building distributed tsunami warning systems.

Abstract. We propose the use of variable resolution boundaries
based on central Voronoi tessellations (CVTs) to spatially aggregate building
exposure models for risk assessment to various natural hazards. Such a
framework is especially beneficial when the spatial distribution of the
considered hazards presents intensity measures with contrasting footprints
and spatial correlations, such as in coastal environments. This work avoids
the incorrect assumption that a single intensity value from hazards with low
spatial correlation (e.g. tsunami) can be considered to be representative
within large-sized geo-cells for physical vulnerability assessment, without,
at the same time, increasing the complexity of the overall model. We present
decoupled earthquake and tsunami scenario-based risk estimates for the
residential building stock of Lima (Peru). We observe that earthquake loss
models for far-field subduction sources are practically insensitive to the
exposure resolution. Conversely, tsunami loss models and associated
uncertainties depend on the spatial correlations of the hazard intensities
as well as on the resolution of the exposure models. We note that for the
portfolio located in the coastal area exposed to both perils in Lima, the
ground shaking dominates the losses for lower-magnitude earthquakes, whilst
tsunamis cause the most damage for larger-magnitude events. For the latter,
two sets of existing empirical flow depth fragility models are used,
resulting in large differences in the calculated losses. This study,
therefore, raises awareness about the uncertainties associated with the
selection of fragility models and spatial aggregation entities for exposure
modelling and loss mapping.

Abstract. Tsunamis caused by large volcanic eruptions and flanks collapsing into the
sea are major hazards for nearby coastal regions. They often occur with
little precursory activity and are thus challenging to detect in a timely
manner. This makes the pre-emptive identification of volcanoes prone to
causing tsunamis particularly important, as it allows for better hazard
assessment and denser monitoring in these areas. Here, we present a
catalogue of potentially tsunamigenic volcanoes in Southeast Asia and rank
these volcanoes by their tsunami hazard. The ranking is based on a
multicriteria decision analysis (MCDA) composed of five individually
weighted factors impacting flank stability and tsunami hazard. The data are sourced from geological databases, remote sensing data, historical volcano-induced tsunami records, and our topographic analyses, mainly considering the eruptive and tsunami history, elevation relative to the distance from the sea, flank steepness, hydrothermal alteration, and vegetation coverage. Out of 131 analysed volcanoes, we found 19 with particularly high
tsunamigenic hazard potential in Indonesia (Anak Krakatau, Batu Tara,
Iliwerung, Gamalama, Sangeang Api, Karangetang, Sirung, Wetar, Nila, Ruang,
Serua) and Papua New Guinea (Kadovar, Ritter Island, Rabaul, Manam, Langila, Ulawun, Bam) but also in the Philippines (Didicas). While some of these volcanoes, such as Anak Krakatau, are well known for their deadly tsunamis, many others on this list are lesser known and monitored. We further performed tsunami travel time modelling on these high-hazard volcanoes, which indicates that future events could affect large coastal areas in a short time. This highlights the importance of individual tsunami hazard assessment for these volcanoes, the importance of dedicated volcanological monitoring, and the need for increased preparedness on the potentially affected coasts.

Abstract. The initial conditions for the simulation of a seismically induced tsunami for a rapid, assumed-to-be-instantaneous vertical seafloor displacement is given by the Kajiura low-pass filter integral. This work proposes a new, efficient, and accurate approach for its numerical evaluation, valid when the seafloor displacement is discretized as a set of rectangular contributions over variable bathymetry. We compare several truncated quadrature formulae, selecting the optimal one. The reconstruction of the initial sea level perturbation as a linear combination of pre-computed elementary sea surface displacements is tested on the tsunamigenic Kuril earthquake doublet – a megathrust and an outer rise – that occurred in the central Kuril Islands in late 2006 and early 2007. We also confirm the importance of the horizontal contribution to tsunami generation, and we consider a simple model of the inelastic deformation of the wedge on realistic bathymetry. The proposed approach results are accurate and fast enough to be considered relevant for practical applications. A tool to build a tsunami source database for a specific region of interest is provided.

Tsunamis are unpredictable and infrequent but potentially large impact natural disasters. To prepare, mitigate and prevent losses from tsunamis, probabilistic hazard and risk analysis methods have been developed and have proved useful. However, large gaps and uncertainties still exist and many steps in the assessment methods lack information, theoretical foundation, or commonly accepted methods. Moreover, applied methods have very different levels of maturity, from already advanced probabilistic tsunami hazard analysis for earthquake sources, to less mature probabilistic risk analysis. In this review we give an overview of the current state of probabilistic tsunami hazard and risk analysis. Identifying research gaps, we offer suggestions for future research directions. An extensive literature list allows for branching into diverse aspects of this scientific approach. © Copyright © 2021 Behrens, Løvholt, Jalayer, Lorito, Salgado-Gálvez, Sørensen, Abadie, Aguirre-Ayerbe, Aniel-Quiroga, Babeyko, Baiguera, Basili, Belliazzi, Grezio, Johnson, Murphy, Paris, Rafliana, De Risi, Rossetto, Selva, Taroni, Del Zoppo, Armigliato, Bureš, Cech, Cecioni, Christodoulides, Davies, Dias, Bayraktar, González, Gritsevich, Guillas, Harbitz, Kânoǧlu, Macías, Papadopoulos, Polet, Romano, Salamon, Scala, Stepinac, Tappin, Thio, Tonini, Triantafyllou, Ulrich, Varini, Volpe and Vyhmeister. ; This article is based upon work from COST Action CA18109 AGITHAR, supported by COST (European Cooperation in Science and Technology). VB and PC obtained support through the VES20 Inter-Cost LTC 20020 project. MS-G obtained support through the Severo Ochoa Centers of Excellence Program (Ref. CEX 2018–000797-S). TU acknowledges funding from the European Union's Horizon 2020 research and innovation program (ChEESE project, Grant Agreement No. 823844).