Tsunami Source Research Articles

Analysis of recent atypical tsunami source events worldwide and their implications for tsunami research in the South China Sea

Analysis of recent atypical tsunami source events worldwide and their implications for tsunami research in the South China Sea

Potential Volcanic Origin of the 2023 Short-period Tsunami in the Izu Islands, Japan

On October 8, 2023, at 21:40 UTC (6:40 on October 9 local time), a tsunami warning was issued for the Izu Islands and southwest Japan. This tsunami was initially considered to be associated with the Mw 4.7 earthquake at 20:25 UTC (5:25 JST). However, we know events of this magnitude are far too small to generate observed tsunamis from coseismic deformation alone. In this study, we analyzed the ocean-bottom pressure records of DONET and S-net, real-time cabled observation networks on the Pacific coast of Japan. We find that the dominant period of this tsunami was relatively short, 250 sec, and that the largest tsunami occurred at 21:13 (6:13 JST) near Sofu-gan volcano. In addition, T waves, or the ocean-acoustic waves, were clearly observed by DONET – we posit these correspond to a vigorous swarm-like seismic event at the same region of the tsunami source. We formally invert for the tsunami source and find that several tsunami sources with an interval of about 4 min are necessary to reproduce the observed records. These most likely correspond to volcanic eruptions.

Adjoint Inversion of Near‐Field Pressure Gauge Recordings for Rapid and Accurate Tsunami Source Characterization

AbstractWe explore the potential of the adjoint‐state tsunami inversion method for rapid and accurate near‐field tsunami source characterization using S‐net, an array of ocean bottom pressure gauges. Compared to earthquake‐based methods, this method can obtain more accurate predictions for the initial water elevation of the tsunami source, including potential secondary sources, leading to accurate water height and wave run‐up predictions. Unlike finite‐fault tsunami source inversions, the adjoint method achieves high‐resolution results without requiring densely gridded Green's functions, reducing computation time. However, optimal results require a dense instrument network with sufficient azimuthal coverage. S‐net meets these requirements and reduces data collection time, facilitating the inversion and timely issuance of tsunami warnings. Since the method has not yet been applied to dense, near‐field data, we test it on synthetic waveforms of the 2011 Mw 9.0 Tohoku earthquake and tsunami, including triggered secondary sources. The results indicate that with a static source model without noise, using the first 5 min of the waveforms yields a favorable performance with an average accuracy score of 93%, and the largest error of predicted wave amplitudes ranges between −5.6 and 1.9 m. Using the first 20 min, secondary sources were clearly resolved. We also demonstrate the method's applicability using S‐net recordings of the 2016 Mw 6.9 Fukushima earthquake. The findings suggest that lower‐magnitude events require a longer waveform duration for accurate adjoint inversion. Moreover, the estimated stress drop obtained from inverting our obtained tsunami source, assuming uniform slip, aligns with estimations from recent studies.

Forward numerical investigation of potential tsunami deposits in the South China sea: A case study of Nan'ao Island

The South China Sea (SCS) coastlines are particularly vulnerable to tsunamis due to rapid urbanization and dense infrastructures. However, whether the SCS has experienced ocean-wide tsunamis is still under debate. Some geological records from the offshore islands inside the SCS imply a regional tsunami event may have occurred approximately 1000-yr-ago. We address these questions for the first time using forward numerical simulations in the SCS: what source could be responsible for such deposits, how the deposits were formed and at what conditions do the deposits could be preserved? Here, we assume the validity of the tsunami deposit hypothesis and use the forward model COMCOT-SED to investigate if these tsunami deposits can be linked to potential seismogenic tsunami sources inside the SCS, including megathrust earthquakes (Mw8.8–9.2) from the Manila subduction zone (MSZ) and the 1918 Mw7.5 Nan'ao earthquake from the Littoral Fault Zone (LFZ) in the northern continental shelf of the SCS. We also utilize a reported tsunami deposit from Qing'ao Embayment, Nan'ao Island, China, to exemplify the deposit formation process in a typical barrier-low coastal plain system. Quantitative analysis suggests large earthquakes from the MSZ may account for the reported geological deposits. The full-rupture earthquake scenario could best explain the depositions if such extreme case is geophysically and geologically plausible. If not, earthquakes (∼ Mw 9.0) covering the northern (16–23.5°N) or southern portion (14–19°N) of the MSZ could also be suitable candidates. Such great earthquakes can generate large tsunami waves (>7 m) that inundate the Qing'ao Embayment, transporting sediments and leaving tsunami deposits in low-lying areas. Conversely, tsunamis triggered by nearshore earthquakes in the LFZ cannot cause deposition in Qing'ao Embayment. The barrier-low coastal plain system is well-suited for preserving tsunami deposits, which remain unaltered by subsequent tsunami waves. Our findings offer a quantitative reference for paleo-tsunami research in the SCS and enhance global understanding of the tsunami deposition process in barrier-low coastal plain systems.

Tsunami potential in the Makran subduction zone: Amplification effects from earthquake rupture directivity and speed

Tsunami potential in the Makran subduction zone: Amplification effects from earthquake rupture directivity and speed

Deformation Anomalies Accompanying Tsunami Origins near the Japanese Islands

In the paper, we analyze laser strainmeter data for the period from 2014 to 2022 to identify deformation anomalies that led to the generation of tsunamis in the area of the Japanese Islands. It is impossible to determine the main characteristics of a tsunami from the deformation anomaly registered by the laser strainmeter, but it is possible to calculate the seabed displacement in the epicenter of a tsunami formation, which causes the tsunami. We have established that the relationship between the registered deformation anomalies and the seabed displacement in the tsunami source in the area of the Japanese Islands is similar to the same relationships found in other regions of the Earth (Indonesia, Latin America, and the West Coast of North America). This result allows us to assert that such a relationship should be typical of any region of the Earth. The obtained results are aimed at solving the problem of reliable short-term tsunami forecasting, which allows for the avoidance of false alarms that lead to significant socio-economic damage.

Submarine landslide-induced tsunami generation in Makassar strait, Indonesia using Non-hydrostatic wave model

Tsunami modelling of potential landslide-induced tsunami in Makassar Strait is carried out to quantify possible damage to the nearby cities. The numerical model is used to represent the wave generation by using NHWAVE model. The simulations consist of a series of scenarios based on distinct size of the landslide volume. Four landslides with volume 5, 8, 70, and 200 km3 are used as tsunami sources in the initiation stage. The sources are evenly distributed in the strait addressing different landslide location. Maximum wave heights of 1.5 m are found in the area between Palu and Bangkir from case 1 and around Talok from case 2 simulations. The empirical run-up calculation of 7.5 m is estimated at the land for the presented wave height. The value significantly elevates the case 3 and 4 proportional to the volume values. The waves impact more than half of coastline with maximum value found in the Sulawesi side. Interestingly, wide and narrow shelf next to Kalimantan Island plays an important role in reducing the tsunami hazard level.

Origins of the Tsunami Following the 2023 Turkey–Syria Earthquake

AbstractOn 6 February 2023, a local tsunami was recorded in the southeastern Mediterranean Sea following the Mw 7.7 Turkey–Syria inland strike‐slip earthquake. Due to the lack of underwater observation, the tsunami generation mechanism remains mysterious. To understand the source mechanisms, we analyzed the tsunami waveforms of four nearby tide gauges and located possible sources using a backward tsunami ray tracing approach. We then conducted forward numerical modelings for a range of possible source parameters. We show that there were probably two tsunami sources, inside and outside Iskenderun Bay, which may be related to thick coastal sediments. A source inside the Bay with a characteristic length of 7 km produced dominant periods of 10–30 min with negative initial motion, possibly generated by a landslide. Another source of 6 km length outside the Bay produced dominant periods of 2–10 min with positive initial motions, possibly related with liquefaction.

Studi Potensi Tsunami Bali Utara Menggunakan Metode Numerik


 
 
 
 Bali Island is one of the most tsunami-prone areas in Indonesia. Two tectonic tsunami sources flank Bali Island: The Megathurst subduction zone in the south and the Back Arc Thurst subduction zone in the north. This study aimed to add information about the tsunami arrival time and the maximum height of the tsunami waves that hit the coast using COMCOT software as a disaster mitigation measure. Five scenarios were used in this study with the differences in the magnitude of tsunami-generating earthquakes. Results showed that the fastest affected shoreline by the tsunami in scenarios 1, 2, and 3 is the Tejakula Sub District shoreline, with a period of 5 minutes 41 seconds to 3 minutes 43 seconds. In scenarios 4 and 5, it was found on the Sawan Sub District shoreline for 2 minutes, 51 seconds to 56 seconds. The maximum run-up of tsunami waves that hit the shoreline in scenarios 1, 2, 3, and 4 are on the Kubu Sub District shoreline with run-up heights of 0.0095 m, 0.47 m, 1.5 m, and 3 m. In scenario 5, the highest run-up is on the Banjar Sub District shoreline, with a 67.6 m run-up height. Based on the results of this study, it can be concluded that the magnitude of the tsunami-generating earthquake greatly influences the travel time and run-up height of the tsunami waves. The greater the magnitude of the tsunami-generating earthquake, the faster the travel time of the tsunami waves and the higher the run-up height.
 
 
 

Sensitivity of slip distribution on tsunami trace heights and geological evidences: a case study of the 2011 Tohoku-Oki earthquake

We examined whether it is possible to estimate the tsunami source model of the 2011 Tohoku-Oki earthquake from a comparison of numerical simulations of tsunami propagation and sediment transport, the measured trace heights, and the sediment thickness of tsunami deposits. Twelve models with different subfault numbers were prepared based on a reference model inferred from tsunami waveform inversion. The reference model with 55 subfaults considering rupture propagation and the model with instantaneous slip successfully reproduced both the tsunami trace heights and sediment thickness distribution of tsunami deposits in the Idagawa Lowland and Sendai Plain. Other models with the same moment magnitude but fewer subfaults could not reproduce the observed trace heights, and the reproducibility of sediment thickness distribution strongly depended on the slip distribution. Models with increased slip amounts and moment magnitude could reproduce the trace heights; however, the simulated sediment thickness was underestimated for the Idagawa Lowland while overestimated for the Sendai Plain. Our results indicate that the combination of trace heights, sediment thickness of tsunami deposits, and numerical simulations of tsunami propagation and sediment transport can be used to estimate historical earthquakes and tsunamis. Efforts should be made to increase the number of subfaults for the study of historical events, although the obtained solutions may not be unique because of fewer trace heights or tsunami deposit data.

On the use of tsunami-source data for high-resolution fault imaging of offshore earthquakes

The source imaging for offshore earthquakes using terrestrial geodetic data has a limited estimation performance due to the low data resolution. One approach to overcome this limitation is the use of seafloor geodetic data. In this study, we focus on tsunami-source data, which is the spatial distribution of vertical crustal displacements above the source area and can be derived from tsunami waveform records. We evaluate how the use of this spatial seafloor geodetic data improves the estimation of a rectangular fault model. Here, the fault model of the 2016 off-Fukushima earthquake in Japan, which was a shallow intraplate earthquake (Mw 7.0), was estimated by three inversions: terrestrial Global Navigation Satellite System (GNSS) data only, tsunami-source data only, and a combination of the GNSS data and tsunami-source data. A Bayesian inversion approach was used to understand the distribution of the estimated fault parameters and their relationship. The results indicated that the terrestrial GNSS data have a low resolution for the analysis of the offshore earthquake, which resulted in a biased solution with large uncertainty. Conversely, the use of tsunami-source data significantly improved the resolution and reliability of source imaging and reduced the dependency among fault parameters. These results suggested that the high-spatial-resolution information of tsunami source is a powerful tool in source imaging of offshore shallow earthquakes. Moreover, the combined use of the two different geodetic data leads to a more robust estimation of fault parameters. We believe that the use of tsunami-source data is useful, not only for the post hoc source analysis, but also for estimating an earthquake rupture area just after a large earthquake, where GNSS data are currently used.Graphical

Criterion of Applicability of the Theory of Long Waves for Description of Dispersive Tsunami Waves

Conditions for the applicability of the dispersionless theory of long waves for reproducing dispersive tsunami waves are analyzed. As a quantitative criterion, the dispersive destruction distance is proposed for use, which is a value that is uniquely determined by the wavelength that dominates in the spectrum of the initial elevation of the water surface in the tsunami source, and the correction factor \(\alpha .\) The physical meaning of the \(\alpha \) value is the fraction of the wavelength by which the dispersive wave packet lags behind the long wave front when propagating over a distance equal to the dispersive destruction distance. Using the model residual displacement of the bottom surface, the geometrical parameters of which vary randomly, under the assumption of instantaneous generation of waves and taking into account the smoothing effect of the water layer, the Monte Carlo method establishes a relationship between the accuracy of wave reproduction by the dispersionless model and the quantity \(\alpha .\) Using the “\(\alpha \) coefficient scale”, the ranking of the criteria that were previously proposed by other authors was performed.

Determining the Success of Strong Motion Records in Calculating P-Wave Moment Magnitude

Earthquake early warning systems have high importance and improving continuously using different analysing techniques. The system depends on calculating a magnitude in a short time with as high accuracy as possible. Large earthquakes that have tsunami potential occurred and will be occurred especially in the Mediterranean and Aegean Seas Turkey has settlements along these coastlines. In practice, weak-motion (velocity) records are generally used to determine the magnitude, but these seismic records have a disadvantage: a clipping problem around the epicentre. Up to now, there is not much work on the study of the strong-motion (acceleration) records to calculate the magnitude of an earthquake in a short time with high accuracy. This study focused on calculating the P-wave moment magnitude using P-wave body waves recorded at strong motion seismic stations caused by possible tsunami source region earthquakes. For that reason, we used three earthquakes that have a magnitude larger than 6.0 Mw. The difference between the Global Centroid Moment Tensor (GCMT) moment magnitude is about 0.2 m.u. which is acceptable considering an early warning purpose.

Reducing the vulnerability of tourists to tsunami: challenges for decision-makers

A near source or local tsunami, because of its close proximity to an affected area, cannot usually be predicted soon enough to mitigate many of the risks posed. The limited notice time in local tsunamis poses greater challenges for decision-makers than distant source tsunamis. Tsunamis affect coastal regions, where many of these areas are visited by tourists who often lack adequate knowledge of the hazards of the region. This study focuses on the risks tourists face during a local tsunami and discusses how to best protect tourists. Initially, a thematic literature analysis was performed to identify research gaps. Then, a case study methodology was adopted to obtain an in-depth understanding of how emergency management officials consider the management of tourists in evacuation planning. Napier, New Zealand, was used as a case study because it is a tourist town and vulnerable to tsunamis. Key decision-makers in the disaster management and tourist management sector were interviewed. The results outline three major initiatives that could lead to better tourist management and create better tsunami awareness for tourists. First, the risks posed to tourists can be reduced if emergency management officials collaborate with tourism agencies. Second, developing accurate evacuation simulations can show what would happen to tourists in a tsunami so that emergency management officials can be better prepared, and councils can improve evacuation planning and infrastructure to evacuate tourists and local communities safely. Third, educating tourists about evacuation plans will increase their readiness and enhance their safety.

Seismogenic potential and tsunami threat of the strike-slip Carboneras fault in the western Mediterranean from physics-based earthquake simulations

Abstract. Strike-slip fault ruptures have a limited capacity to generate vertical deformation, and for this reason they are usually dismissed as potential destructive tsunami sources. At the western tip of the western Mediterranean, in the Alboran Sea, tectonics is characterized by the presence of large transcurrent fault systems and minor reverse and normal faults in a zone of diffuse deformation. The strike-slip Carboneras fault is one of the largest sources in the Alboran Sea and therefore with the greatest seismogenic capacity. It is also one of the active structures with higher slip rates in the eastern Betic fault zone and has been proposed as the source of the damaging 1522 (M 6.5; Int. VIII–IX) Almeria earthquake. The dimensions and location of the Carboneras fault imply a high seismic and tsunami threat. In this paper we present tsunami simulations from seismic sources generated with physics-based earthquake simulators. We have generated a 1 Myr synthetic seismic catalogue consistent on 773 893 events, with magnitudes ranging between Mw 3.3 and 7.6. From these events we have selected those sources producing a potential energy capable of generating a noticeable tsunami, those sources being earthquakes with magnitudes ranging from 6.71 to 7.62. The Carboneras fault has the capacity to generate locally damaging tsunamis; however, on a regional scale its tsunami threat is limited. The frequency–magnitude distribution of the generated seismic catalogue reflects the variability of magnitudes associated with the rupture of the entire fault, departing the upper limit from the classical Gutenberg–Richter potential relation. The inter-event time for the maximum earthquake magnitudes is usually between 2000 and 6000 years. The use of physics-based earthquake simulations for tsunamigenic sources allows an in-depth characterization of the scenarios, allowing a qualitative leap in their parametrization.

Geological evidence of predecessor of the 2018 Tsunami in Palu, Sulawesi, Indonesia

Following the 2018 Palu tsunami event in Central Sulawesi, Indonesia, the geological evidence of paleotsunami in Palu, was investigated to extend the historical record of past tsunamis in this area. A geological survey was conducted in Talise Beach, Palu City, at the southern end of Palu Bay. The stratigraphy sequence from the outcrop profile in Talise Beach showed three clear paleotsunamis. These paleotsunamis are distributed widely and can be traced along 1 ​km parallel to the beach, and each layer is characterized by poorly sorted sand deposited on the paleosoil. The boundary between the sand layers and paleosoils is sharp and erosional. The sedimentological and foraminifera analyses support the identification of paleotsunamis. Based on the radiocarbon dating, it was interpreted that these three paleotsunamis occurred in the 17th, 18th, and 19th century. This first paleotsunami study in Palu, not only provided geological evidence of paleotsunamis, and extended the tsunami record in Palu, but also served as an essential start for tsunami geology study in Palu as the tsunami sources in this area are complex.

Improving Efficacy of Tsunami Warnings Along the West Coast of the United States

Tsunamis cause significant damage and loss of life, particularly for the nearest communities, where the tsunami may arrive in minutes. These local communities often do not receive an informed or timely alert under traditional warning pathways. In response, numerous tsunami early warning (TEW) algorithms have been developed with the goal of providing informed tsunami source characterization for use in rapid, localized warning. An overlooked aspect of TEW is the means that this crucial information is disseminated. Current operations focus heavily on the time an alert is issued from a warning center, however, that alert passes through multiple groups and agencies before it is conveyed to affected communities. This distribution path can create further delays and contributes to inconsistencies in the message timeliness and content. In this study, we provide the framework and advocate for the use of a rapid dissemination tool, that we call WaveAlert, that would leverage preexisting advances in earthquake early warning systems to provide timely, clear, and consistent alerts to the public by use of the MyShake EEW phone app. This proposed tsunami dissemination tool would be able to provide consistent, public facing tsunami alerts over the duration of the hazard with the added benefit of low message latencies and high spatial resolution in who can be targeted for messages. We illustrate the need for rapid alerting strategies through a retrospective look at the alerting process during the 2022 Tonga tsunami and through a modeled potential near-field Cascadia timeline example affecting the west coast of the US.

Assessing probability of building damages due to tsunami hazards coupled with characteristics of buildings in Banda Aceh, Indonesia: A way to increase understanding of tsunami risks

Knowing the potential number of buildings that could be damaged by a future tsunami is important in understanding tsunami risk. There is a limited number of studies that combine the tsunami inundation area that is generated based on probabilistic tsunami hazard analysis and tsunami fragility curves. This study is aimed at providing information on probabilistic tsunami hazard for the city of Banda Aceh (Indonesia), whereby the results could possibly be integrated into tsunami risk reduction in the city. A series of numerical simulations were performed using the Cornell Multi-Grid Coupled Tsunami Model (COMCOT). Tsunami sources were taken from rupture areas generated by a set of earthquakes emanating from the Aceh-Andaman Megathrust segment. Later, tsunami inundation areas that were produced from numerical simulations were used in a probabilistic hazard analysis. This research produced three sets of tsunami inundation maps for 250-, 500-, and 1000-year return event periods. Hazard curves were produced based on 230,000 grids. Field surveys were performed in order to assess over 82,000 building units in Banda Aceh, and classified them into six types of buildings, in accordance with HAZUS (Hazards United States). Based on two sets data of buildings in Banda Aceh (measured in 2017 and 2021), there has been an increased number of buildings in the city by around 31%. Most of the new buildings were identified as houses. A set of tsunami fragility curves was used to estimate the damage ratio of each of the buildings. It was found that around 10.5% of the buildings (8708 units of buildings) would likely be totally demolished (swept away), should a 1000-year return period tsunami occur. Inundation maps produced for the 1000-year return period tsunami found in this study portray a similar situation to that of the 2004 Indian Ocean tsunami.

Scenario-based modelling of waves generated by sublacustrine explosive eruptions at Lake Taupō, New Zealand

Abstract. Volcanogenic tsunami and wave hazard remains less understood than that of other tsunami sources. Volcanoes can generate waves in a multitude of ways, including subaqueous explosions. Recent events, including a highly explosive eruption at Hunga Tonga-Hunga Ha'apai and subsequent tsunami in January 2022, have reinforced the necessity to explore and quantify volcanic tsunami sources. We utilise a non-hydrostatic multilayer numerical method to simulate 20 scenarios of sublacustrine explosive eruptions under Lake Taupō, New Zealand, across five locations and four eruption sizes. Waves propagate around the entire lake within 15 min, and there is a minimum explosive size required to generate significant waves (positive amplitudes incident on foreshore of > 1 m) from the impulsive displacement of water from the eruption itself. This minimum size corresponds to a mass eruption rate of 5.8×107 kg s−1, or VEI 5 equivalent. Inundation is mapped across five built areas and becomes significant near shore when considering only the two largest sizes, above VEI 5, which preferentially impact areas of low-gradient slope. In addition, novel hydrographic output is produced showing the impact of incident waves on the Waikato River inlet draining the lake and is potentially useful for future structural impact analysis. Waves generated from these explosive source types are highly dispersive, resulting in hazard rapidly diminishing with distance from the source. With improved computational efficiency, a probabilistic study could be formulated and other, potentially more significant, volcanic source mechanisms should be investigated.

A stochastic approach to the characterization of the seismic sources: a potential method for the assessment of sources of historical and paleo tsunami

A stochastic approach to the characterization of the seismic sources: a potential method for the assessment of sources of historical and paleo tsunami