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Tsunamis generated by underwater volcanic eruptions are physically modeled in a large three-dimensional wave basin. A unique pneumatic volcanic tsunami generator (VTG) was deployed at the bottom of the wave basin to generate volcanic tsunamis with repeatable source parameters under controlled physical conditions. The volcanic Froude number defined with the VTG eruption velocity and water depth allows to physically model real-world events from slow mud-volcanoes to explosive eruptions. The VTG generates radial N-waves with prescribed vertical stroke motions in the wave basin. Initial three-dimensional water surfaces are reconstructed for the daylighting scenarios. Smooth dome shapes are observed during the submarine volcanic eruption and tsunami wave generation, which is followed by a trough formation at the source. A concentric vertical spike is observed for a specific range of water depths, which is generated by superposition of an inward propagating circular bore on top of the wave generator. The spike can be clustered with different ranges of a dimensionless VTG parameter. With an increasing dimensionless parameter, the spike pattern transitions through three distinct categories: smooth spike, rough spike, and splash spike. The dimensionless spike height and the dimensionless vertical velocity of the spike tip are dependent on the dimensionless VTG parameters. The maximum values of the dimensionless spike height and spike tip velocity are observed in the rough spike regime among all tested experimental scenarios. [ABSTRACT FROM AUTHOR]

On December 22, 2018, the eruption and flank collapse of the Anak Krakatau volcano generated a tsunami in the Sunda Strait causing catastrophic damage to uninhabited coastlines proximal to the source. Along the heavily populated shores of Banten and Lampung provinces in Java and Sumatra, tsunami waves caused severe damage, extensive inundation and more than 430 deaths. An international tsunami survey team (ITST) deployed 6 weeks after the event documented the tsunami effects including runup heights, flow depths and inundation distances, as well as sediment deposition patterns and impacts on infrastructure and the natural environment. The team also interviewed numerous eyewitnesses and educated residents about tsunami hazards. This ITST was the first to visit and document the extreme tsunami effects on the small islands in the Sunda Strait closest to Anak Krakatau (Rakata, Panjang, Sertung, Sebesi and Panaitan). Along the steep slopes of Rakata and Sertung islands, located less than 5 km from and facing directly towards the southwest flank of Anak Krakatau, all of the dense coastal vegetation was stripped to bare earth up to elevations of more than 80 m, while on the northeast tip of Sertung Island, facing away from the source, a single tree remained standing after flow depths of > 11 m above ground struck there. The runup distributions on the islands encircling Anak Krakatau highlight the directivity of the tsunami source suggesting that the collapse occurred towards the southwest. This manifested as tsunami runup of < 10 m on Sebesi Island, located 15 km northeast of the source, contrasting with tsunami flow heights > 10 m that stripped away coastal forests to bare rock for up to 400 m inland in the Ujung Kulon National Park, located 50 km to the south-southwest. Inundation and damage were mostly limited to within 400 m of the shoreline, likely the result of the relatively short wavelengths caused by the landslide generated tsunami. A significant variation in tsunami impact was observed along the shorelines of the Sunda Strait, with runup heights rapidly decreasing with distance from the inferred tsunami source. To model the event we applied a hot-start initial condition that roughly reproduced the measured tsunami runup heights along Rakata and Sertung. The waveforms were then propagated through the Sunda Straight using a Boussinesq-type wave model. The results showed a good fit to the observed heights along the Java and Sumatra coastlines, the northern coast of Panaitan Island and Ujung Kulon Nation Park. The model also produced an acceptable fit to the observed amplitudes at tide gauges. Despite the regional volcanic and tsunamigenic history of the region, and 6-months of eruptive activity prior to the event, the tsunami largely caught the local population off guard. This further highlights the need for community-based education and awareness programs as essential to save lives in locales at risk from locally generated tsunamis. [ABSTRACT FROM AUTHOR]

After more than a decade of recurring tsunamis, identification of tsunami deposits, a part of hazard characterization, still remains a challenging task that is not fully understood. The lack of sufficient monitoring equipment and rare tsunami frequency are among the primary obstacles that limit our fundamental understanding of sediment transport mechanisms during a tsunami. The use of numerical simulations to study tsunami-induced sediment transport was rare in Indonesia until the 2004 Indian Ocean tsunami. This study aims to couple two hydrodynamic numerical models in order to reproduce tsunami-induced sediment deposits, i.e., their locations and thicknesses. Numerical simulations were performed using the Cornell Multi-grid Coupled Tsunami (COMCOT) model and Delft3D. This study reconstructed tsunami wave propagation from its source using COMCOT, which was later combined with Delft3D to map the location of the tsunami deposits and calculate their thicknesses. Two-dimensional horizontal (2-DH) models were used as part of both simulation packages. Four sediment transport formulae were used in the simulations, namely van Rijn 1993, Engelund–Hansen 1967, Meyer-Peter–Mueller (MPM) 1948, and Soulsby 1997. Lhoong, in the Aceh Besar District, located approximately 60 km southwest of Banda Aceh, was selected as the study area. Field data collected in 2015 and 2016 validated the forward modeling techniques adopted in this study. However, agreements between numerical simulations and field observations were more robust using data collected in 2005, i.e., just months after the tsunami (Jaffe et al., 2006). We conducted pit (trench) tests at select locations to obtain tsunami deposit thickness and grain size distributions. The resulting numerical simulations are useful when estimating the locations and the thicknesses of the tsunami deposits. The agreement between the field data and the numerical simulations is reasonable despite a trend that overestimates the field observations. [ABSTRACT FROM AUTHOR]

Landslides of subaerial and submarine origin may generate tsunamis with locally extreme amplitudes and runup. While the landslides themselves are dangerous, the hazards are compounded by the generation of tsunamis along coastlines, in enclosed water bodies, and off continental shelves and islands. Tsunamis generated by three-dimensional deformable granular landslides were studied on planar and conical hill slopes in the three-dimensional NEES tsunami wave basin at Oregon State University based on the generalized Froude similarity. A unique pneumatic landslide tsunami generator (LTG) was deployed to control the kinematics and acceleration of the naturally rounded river gravel and cobble landslides to simulate broad ranges of landslide shapes and velocities along the slope. Lateral and overhead cameras are used to measure the landslide shapes and kinematics, while acoustic transducers provide the shape of the subaqueous deposits. The subaerial landslide shape is extracted from the camera images as the landslide propagates under gravity down the hill slope, and surface reconstruction of the landslide is conducted using the stereo particle image velocimetry (PIV) system on the conical hill slope. Subaerial landslide surface velocities are measured with a planar PIV system on the planar hill slope and stereo PIV system on the conical hill slope. The submarine deposits are characterized by the runout distances and the deposit thickness distributions. Larger cobbles are observed producing hummock type features near the maximum runout length. These unique laboratory landslide experiments serve to validate deformable landslide models as well as provide the source characteristics for tsunami generation. [ABSTRACT FROM AUTHOR]

Twenty papers on the study of tsunamis are included in Volume III of the PAGEOPH topical issue “Global Tsunami Science: Past and Future”. Volume I of this topical issue was published as PAGEOPH, vol. 173, No. 12, 2016 and Volume II as PAGEOPH, vol. 174, No. 8, 2017. Two papers in Volume III focus on specific details of the 2009 Samoa and the 1923 northern Kamchatka tsunamis; they are followed by three papers related to tsunami hazard assessment for three different regions of the world oceans: South Africa, Pacific coast of Mexico and the northwestern part of the Indian Ocean. The next six papers are on various aspects of tsunami hydrodynamics and numerical modelling, including tsunami edge waves, resonant behaviour of compressible water layer during tsunamigenic earthquakes, dispersive properties of seismic and volcanically generated tsunami waves, tsunami runup on a vertical wall and influence of earthquake rupture velocity on maximum tsunami runup. Four papers discuss problems of tsunami warning and real-time forecasting for Central America, the Mediterranean coast of France, the coast of Peru, and some general problems regarding the optimum use of the DART buoy network for effective real-time tsunami warning in the Pacific Ocean. Two papers describe historical and paleotsunami studies in the Russian Far East. The final set of three papers importantly investigates tsunamis generated by non-seismic sources: asteroid airburst and meteorological disturbances. Collectively, this volume highlights contemporary trends in global tsunami research, both fundamental and applied toward hazard assessment and mitigation. [ABSTRACT FROM AUTHOR]

On 17 June 2017, a landslide-generated tsunami reached the village of Nuugaatsiaq, Greenland, leaving four persons missing and presumed dead. Here, we present a preliminary high-resolution analysis of the tsunamigenic landslide scar based on three-dimensional (3D) reconstructions of oblique aerial photographs taken during a post-failure reconnaissance helicopter overflight. Through a 3D quantitative comparison with pre-failure topography, we estimate that approximately 58 million m3 of rock and colluvium (talus) was mobilized during the landslide, 45 million m3 of which reached the fjord, resulting in a destructive tsunami. We classify this event as a “tsunamigenic extremely rapid rock avalanche,” which likely released along a pre-existing metamorphic fabric, bounded laterally by slope-scale faults. Further analysis is required to properly characterize this landslide and adjacent unstable slopes, and to better understand the tsunami generation. [ABSTRACT FROM AUTHOR]

SUMMARY On 2010 January 3 a moment magnitude MW 7.1 earthquake struck the Solomon Islands very near the San Cristobal trench, causing extensive landslides and surprisingly large tsunami waves. Because of the unique proximity of islands to the trench (<20 km) and earthquake, a post-seismic survey successfully identified unexpected widespread coseismic subsidence towards the trench (up to 80 cm), with no discernable post-seismic deformation. Approximately 1000 km from the earthquake ocean-bottom pressure sensors measured 1-2 cm open-ocean tsunami waves. Though spatially limited, the local tsunami wave heights up to 7 m were comparable to the much larger adjacent 2007 MW 8.1 earthquake. The seismically determined focal mechanism, broad-scale subsidence, tsunami amplitude and open ocean wave heights are all explained by an extremely shallow low-angle thrust adjacent to the impinging subduction of the two seamounts near the trench. This event belongs to a potentially new class of shallow 'tsunami earthquakes' that is not identified as deficient in radiated seismic energy. [ABSTRACT FROM AUTHOR]

Abstract: An Mw ≈8.1 earthquake south of the Samoan Islands on 29 September 2009 generated a tsunami that killed 189 people. From 4 to 11 October, an International Tsunami Survey Team surveyed the seven major islands of the Samoan archipelago. The team measured locally focused runup heights of 17m at Poloa and inundation of more than 500m at Pago Pago. A follow-up expedition from 23 to 28 November surveying the three main islands of Tonga''s northernmost Niua group revealed surprising 22m runup and 1km inundation. We analyze the extreme tsunami runup and complex impact distribution based on physical and societal observations combined with numerical modeling. That an outer rise/outer trench slope (OR/OTS) event is responsible for a tsunami disaster in the Pacific calls for care in identifying and defining tsunami hazards. Evacuation exercises conducted in Samoa in the preceding year may have limited the human toll; however, cars were identified as potential death traps during tsunami evacuations. This event highlights the extreme hazards from near source tsunamis when the earthquake''s shaking constitutes the de facto warning, and further underscores the importance of community based education and awareness programs as essential in saving lives. [Copyright &y& Elsevier]

Abstract: Super Cyclone Gonu is the strongest tropical cyclone on record in the Arabian Sea. Gonu caused coastal damage due to storm surge and storm wave impact as well as wadi flooding. High water marks, overland flow depths, and inundation distances were measured in the coastal flood zones along the Gulf of Oman from 1 to 4 August 2007. The high water marks peaked at Ras al-Hadd at the eastern tip of Oman exceeding 5m. The storm surge of Gonu is modeled using the Advanced Circulation Model (ADCIRC). The multi-hazard aspect is analyzed by comparing observations from Cyclone Gonu with the 2004 Indian Ocean Tsunami. [Copyright &y& Elsevier]

On July 10, 1958, an earthquake Mw 8.3 along the Fairweather fault triggered a major subaerial landslide into Gilbert Inlet at the head of Lituya Bay on the southern coast of Alaska. The landslide impacted the water at high speed generating a giant tsunami and the highest wave runup in recorded history. The mega-tsunami runup to an elevation of 524 m caused total forest destruction and erosion down to bedrock on a spur ridge in direct prolongation of the slide axis. A cross section of Gilbert Inlet was rebuilt at 1:675 scale in a two-dimensional physical laboratory model based on the generalized Froude similarity. A pneumatic landslide tsunami generator was used to generate a high-speed granular slide with controlled impact characteristics. State-of-the-art laser measurement techniques such as particle image velocimetry (PIV) and laser distance sensors (LDS) were applied to the decisive initial phase with landslide impact and wave generation as well as the runup on the headland. PIV provided instantaneous velocity vector fields in a large area of interest and gave insight into kinematics of wave generation and runup. The entire process of a high-speed granular landslide impact may be subdivided into two main stages: (a) Landslide impact and penetration with flow separation, cavity formation and wave generation, and (b) air cavity collapse with landslide run-out and debris detrainment causing massive phase mixing. Formation of a large air cavity — similar to an asteroid impact — in the back of the landslide is highlighted. A three-dimenional pneumatic landslide tsunami generator was designed, constructed and successfully deployed in the tsunami wave basin at OSU. The Lituya Bay landslide was reproduced in a three-dimensional physical model at 1:400 scale. The landslide surface velocities distribution was measured with PIV. The measured tsunami amplitude and runup heights serve as benchmark for analytical and numerical models. [ABSTRACT FROM AUTHOR]

Tsunamis are normally associated with submarine earthquakes along subduction zones, such as the 2011 Japan tsunami. However, there are significant tsunami sources related to submarine volcanic eruptions. Volcanic tsunamis, like tectonic tsunamis, typically occur with little warning and can devastate populated coastal areas at considerable distances from the volcano. There have been more than 90 volcanic tsunamis accounting for about 25% of all fatalities directly attributable to volcanic eruptions during the last 250 years. The two deadliest non-tectonic tsunamis in the past 300 years are due to the 1883 Krakatoa eruption in Indonesia with associated pyroclastic flows and Japan's Mount Unzen lava dome collapse in 1792. At the source, volcanic tsunamis can exceed tectonic tsunamis in wave height. There are at least nine different mechanisms by which volcanoes produce tsunamis. Most volcanic tsunami waves have been produced by extremely energetic explosive volcanic eruptions in submarine or near water surface settings, or by flow of voluminous pyroclastic flows or debris avalanches into the sea. The "orange" alert in July 2015 at the Kick 'em Jenny submarine volcano off Granada in the Caribbean Sea highlighted the challenges in characterizing the tsunami waves for a potential submarine volcanic eruption. The recent activity and collapse of the volcanic cone at Anak Krakatau generated tsunami waves that impacted coasts along the Sunda Strait without any prior warnings and caused more than 400 fatalities on December 22, 2018.Source and runup scenarios are physically modeled using generalized Froude similarity in the three dimensional NHERI tsunami wave basin at Oregon State University. A novel volcanic tsunami generator (VTG) was deployed to simulate submarine volcanic eruptions with varying initial submergence and kinematics. The VTG consists of a telescopic eruptive column with an approximate outer diameter of 1.2 m. The top cap of the pressurized eruptive column is accelerated vertically by eight synchronized 80 mm diameter pneumatic pistons with a stroke of approximately 0.3 m. More than 300 experimental runs have been performed in summer 2018, which include around 120 combinations of velocities and water depths. The variable eruption velocities of the VTG mimic relatively slow mud volcanoes and rapid explosive eruptions. The gravitational collapse of the eruptive column represents the potential engulfment and caldera formation. Water surface elevations are recorded by an array of resistance wave gauges. The VTG displacement is measured with an internal linear potentiometer and from above and underwater camera recordings. Water surface reconstruction and kinematics are determined with a stereo particle image velocimetry (PIV) system. Wave runup is recorded with resistance wave gauges along the slope and verified with video image processing. The water surface spike from the concentric collision of wave crest is observed under a limited range of water depths and Froude numbers. The energy conversion rates from the volcanic eruption to the wave train are quantified for various scenarios. The measured volcanic eruption and tsunami data serve to validate and advance three-dimensional numerical volcanic tsunami prediction models. [ABSTRACT FROM AUTHOR]

On September 28, 2018, a magnitude Mw 7.5 earthquake occurred in the neck of Sulawesi's Minahasa peninsula. The combined effects of the earthquake and tsunami caused catastrophic damage and more than 2000 deaths. An international tsunami survey team (ITST) was deployed 3 weeks after the event to document flow depths, runup heights, inundation distances, sediment deposition, damage patterns at various scales, performance of the man-made infrastructure and impact on the natural environment. The 23 to 29 October ITST covered a 100 km stretch of coastline circling the entire Palu Bay and adjacent coastlines along the Makassar Strait. A 200 km long reconnaissance flight with an Indonesian Army Mil Mi-17 helicopter provided oblique aerial photography of impacted sites. The collected field survey data includes 130 tsunami runup and flow depth measurements. The tsunami impact peaked inside Palu Bay with flow depths above ground reaching 6 m and maximum runup heights exceeding 10 m. Inundation and tsunami damage was mostly limited to within 0.5 km of the shoreline except along rivers. A rapid decrease of tsunami heights was observed towards the bay entrance and outside of the Palu Bay along the Makassar Strait coastlines. Two tsunami eyewitness video recording locations inside Palu Bay were surveyed for subsequent video image calibration, tsunami hydrograph and flow velocity analysis. We deployed a Leica BLK360 scanner from the NHERI RAPID facility. We acquired precise topographic data using terrestrial laser scanning (TLS) at selected video sites with multiple scans acquired from different instrument positions. These ground-based LiDAR measurements produce 3-dimensional "point cloud" datasets. Digital photography from 3 scanner-mounted cameras yields full dome panoramic images overlaid on highly accurate point clouds. The main coastal road in Palu was overwashed with flow velocities of more than 7 m/s. Field observations, drone videos, helicopter and satellite imagery are presented. Eyewitnesses interviewed based on established protocols indicate rapid tsunami arrivals within a few minutes of the earthquake. We educated residents about tsunami hazards as community-based education and awareness programs are essential to save lives in locales at risk from locally generated tsunamis. [ABSTRACT FROM AUTHOR]

On September 16, 2015, a M w 8.3 earthquake struck the north-central Chile coast, triggering a tsunami observed along 500 km of coastline, between Huasco (28.5°S) and San Antonio (33.5°S). This tsunami provided a unique opportunity to examine the nature of tsunami deposits in a semi-arid, siliciclastic environment where stratigraphic and sedimentological records of past tsunamis are difficult to distinguish. To improve our ability to identify such evidence, we targeted one of the few low-energy, organic-rich depositional environments in north-central Chile: Pachingo marsh in Tongoy Bay (30.3°S). We found sedimentary evidence of the 2015 and one previous tsunami as tabular sand sheets. Both deposits are composed of poorly to moderately sorted, gray-brown, fine-to medium-grained sand and are distinct from underlying and overlying organic-rich silt. Both sand beds thin (from ∼20 cm to <1 cm) and fine landward, and show normal grading. The older sand bed is thicker and extends over 125 m further inland than the 2015 tsunami deposit. To model the relative size of the tsunamis that deposited each sand bed, we employed tsunami flow inversion. Our results show that the older sand bed was produced by higher flow speeds and depths than those in 2015. Anthropogenic evidence along with 137Cs and 210Pb dating constrains the age of the older tsunami to the last ∼110 years. We suggest that the older sand bed was deposited by the large tsunami in 1922 CE sourced to the north of our study site. This deposit represents the first geologic evidence of a pre-2015 tsunami along the semi-arid north-central Chile coast and highlights the current and continuing tsunami hazard in the region. • First geologic record of pre-2015 tsunami inundation in north-central Chile. • Stratigraphic and grain-size analyses characterize the 2015 and one older tsunami deposit. • 137Cs, 210Pb, and historical analyses show that the older tsunami was deposited in 1922 CE. • Tsunami and tidal modeling show the 1922 tsunami was higher and faster than the 2015 tsunami. [ABSTRACT FROM AUTHOR]