Tsunami Warning Center Research Articles

Tsunami hazard, warning, and risk reduction in Italy and the Mediterranean Sea: state of the art, gaps, and future solutions

Historical catalogues show evidence for about 300 tsunamis in European coastal waters since 1600 BC, and tsunami hazard models like the NEAMTHM18 provide the probability of future inundation from earthquake-induced tsunamis. A recent wake-up call came from the 2020 Mw7.0 Samos-İzmir earthquake and the following moderate, damaging tsunami. Five accredited Tsunami Service Providers (TSPs) run by IPMA (Portugal), CENALT (France), INGV (Italy), NOA (Greece), and KOERI (Turkey), and several national centers monitor the seismicity and provide tsunami alerts in the framework of the UNESCO Tsunami Early Warning and Mitigation System in the North-eastern Atlantic, the Mediterranean and connected seas (NEAMTWS). In this paper, we focus on the state of the art of earthquake-induced tsunami risk reduction and coastal planning in Italy from the perspective of the Centro Allerta Tsunami (CAT), the INGV NTWC (National Tsunami Warning Center) and TSP. We will emphasize some limitations to draw future directions for better preparation and towards the full implementation of the tsunami warning "last-mile".

Probabilistic tsunami forecasting for early warning

Tsunami warning centres face the challenging task of rapidly forecasting tsunami threat immediately after an earthquake, when there is high uncertainty due to data deficiency. Here we introduce Probabilistic Tsunami Forecasting (PTF) for tsunami early warning. PTF explicitly treats data- and forecast-uncertainties, enabling alert level definitions according to any predefined level of conservatism, which is connected to the average balance of missed-vs-false-alarms. Impact forecasts and resulting recommendations become progressively less uncertain as new data become available. Here we report an implementation for near-source early warning and test it systematically by hindcasting the great 2010 M8.8 Maule (Chile) and the well-studied 2003 M6.8 Zemmouri-Boumerdes (Algeria) tsunamis, as well as all the Mediterranean earthquakes that triggered alert messages at the Italian Tsunami Warning Centre since its inception in 2015, demonstrating forecasting accuracy over a wide range of magnitudes and earthquake types.

Probabilistic tsunami hazard and exposure assessment for the pacific islands- Fiji

Tsunami are known to be one of the most powerful and destructive natural hazards to impact low-lying coastal communities. The Republic of Fiji is situated in a complex tectonic setting at the boundary of two active plates in the South-west Pacific; the Indo-Australian and Pacific Plate, making the country highly vulnerable to earthquakes and tsunami. Local and regional source tsunami is a concern for emergency management. This is due to the limited warning time in receiving a tsunami alert and issuing warnings to the public. Fiji's greatest local and regional tsunami hazard risk is from the Tonga-Kermadec trench and South New Hebrides faults. This paper presents the first probabilistic tsunami hazard assessment of a credible 1 in 10,000 year event for Fiji's two largest populated islands, Viti Levu and Vanua Levu. Subsequent to the probabilistic tsunami hazard assessment, this paper presents the results of a tsunami exposure assessment of the population, assets and critical infrastructure vulnerable to tsunami inundation from Tonga-Kermadec and South New Hebrides tsunami sources. This study applies a mix methodology approach, using a combination of hydrodynamic models, probabilistic approaches, Geographic Information Systems and quantitative analysis to determine maximum tsunami heights and exposure to tsunami hazard. Results of the exposure assessment indicates provinces in Vit Levu and Vanua Levu are likely to be susceptible to various tsunami inundation heights, concluding that people and assets in provinces such as Macuata and Tailevuare more vulnerable to tsunami. The results of this study provides valuable information for the Government of Fiji specifically the National Disaster Management Office, Mineral Resources Department, the National Tsunami Warning Centre and at risk communities. This will increase tsunami risk knowledge and will encourage decisive warning times and allow emergency management to make informative decision-making in regards to emergency preparedness and response planning.

Seismically Derived Ground Tilts Related to the 2010 Chilean Tsunami

AbstractDeveloping new ways to observe tsunami contributes to tsunami research. Tidal and deep-ocean gauges are typically used for coastal and offshore observations. Recently, tsunami-induced ground tilts offer a new possibility. The ground tilt signal accompanied by 2010 Mw 8.8 Chilean earthquake were observed at a tiltmeter network in Japan. However, tiltmeter stations are usually not as widely installed as broadband seismometers in other countries. Here, we studied broadband seismic records from Japan’s F-net and found ground tilt signals consistent with previously published tiltmeter dataset for this particular tsunamic event. Similar waveforms can also be found in broadband seismic networks in other countries, such as Taiwan, as well as an ocean-bottom seismometer. We documented a consistent time sequence of evolving back-azimuth directions of the tsunami waves at different stages of tsunami propagation through beamforming-frequency–wavenumber analysis and particle-motion analysis; the outcomes are consistent with the tsunami propagation model provided by the Pacific Tsunami Warning Center. These results shown that dense broadband seismic networks can provide a useful complementary dataset, in addition to tiltmeter arrays and other networks, to study or even monitor tsunami propagation using arrayed methods.

Taitoko, an advanced code for tsunami propagation, developed at the French Tsunami Warning Centers

This paper presents the new version of the operational code used at the Tsunami Warning Centers in French Polynesia and in mainland France. This nested multigrid code solves either the nonlinear shallow water or the weakly nonlinear Boussinesq equations in a spherical or Cartesian coordinates system. The objective is to simulate the propagation of tsunamis both in the context of tsunami early warning and in the context of research. The originality of this code is to simulate the tsunami propagation through a series of nested grids in which the numerical scheme is specified by the user. Three standard finite-difference methods and two finite volume schemes are available to take into account the dispersive nature of waves or to capture flow discontinuities. The performance of the five numerical schemes has been assessed through idealized 1D and 2D test cases. The convergence rate with grid refinement is evaluated for three of these tests. Diffusion and dispersion of the five schemes are evaluated through the 1D far-field propagation in a channel of constant depth. Finally, two-dimensional simulations of the 2011 Japanese tsunami are performed considering a homogeneous tectonic source. Coastal inundation is simulated in the bay of Kamaishi where run-up heights reached 10 m. The ability of the five schemes to propagate trans-Pacific tsunamis is evaluated through comparisons of time series between simulations and observations at DART buoys. In the context of tsunami early warning, numerical results show that standard finite-difference methods reproduce most of the observed time gauges and that numerical errors associated to these schemes are acceptable.

Meteotsunami model forecast: can coastal hazard be quantified in real time?

A modeling study has been conducted to simulate the June 13, 2013 U.S. East Coast meteotsunami event as a test of the model forecast concept. A numerical simulation based on the MOST (Method of Splitting Tsunami) model was employed for the meteotsunami propagation forecast, while the weather radar reflection imagery was used to simulate real-time input data for the atmospheric pressure-induced tsunami generation. The model tsunami was generated by a moving pressure field during 2.87 h of forcing, and the resultant tsunami was then simulated for additional 5.68 h of propagation without any forcing for a total of 8.55 h of meteotsunami evolution from generation to coastal impact. Simulated time series were compared with the measurements from sea-level coastal gages and the Deep-ocean Assessment and Reporting for Tsunami (DART) data. The model is able to reproduce in general the recorded sea-level changes in the deep ocean and at the coast in terms of arrival times and amplitudes. The model was able to predict coastal tsunami impacts that occurred from one to two hours after the model data assimilation phase ended. Therefore, this approach shows promise for developing meteotsunami model forecast capability based on measurements and data assimilation in real time, at least for meteotsunamis generated by fast-moving weather systems visible on radar reflection imagery. All the data used in this study are already available in real time, the MOST model is already implemented as a seismically generated tsunami forecast model at the Tsunami Warning Centers (TWCs), which makes transition of potential meteotsunami forecast capability to warning operations straightforward.

Tweeting Tsunami: Influence and Early Warning in British Columbia

Background Although early warning has been studied on Twitter, research focused on Canada is rare. British Columbia, Canada, is vulnerable to tsunamis, and warning systems are not ubiquitous. Establishing pre-event networks can contribute to understanding early warning dissemination potential in the province. Analysis This study locates a 1,932 follower network for @NWS_NTWC, a Twitter handle for the U.S. National Tsunami Warning Center, and the province’s primary tsunami warning notification account. A profile content analysis identifies stakeholders and maps locations, and a network analysis describes interconnections by role, country, and community type (rural or urban). Conclusion and implications The results describe how networks can optimize warnings via Twitter. Key outcomes include a longitudinal baseline, network-driven decision-making techniques, strategies for alerting at-risk areas, and a method for detecting influential users.

Numerical Simulation Studies about the Resonance of Tsunami Waves in Selected Gulfs and Ports along the South West Coast of India (SWCI)

The tsunami of December 26, 2004 was an eye-opener which exposed the need for establishing a tsunami warning system in the Indian Ocean. Immediately after the tsunami of 2004, Government of India subsequently established a Tsunami Warning Centre in Hyderabad. The numerical modelling of tsunami inundation and run-up also gained momentum in India. Besides inundation and run-up there are several other physical oceanographic processes which contributes in shaping tsunami characteristics along the coast. The source of tsunami generation is prominent in determining run-up values. Historical records show the generation of tsunamigenic earthquakes from Sumatra, North Andaman and Car Nicobar in the Bay of Bengal and Makran in the Arabian Sea. Though the numerical modelling studies has been reasonably carried out for the main land coast, no study has been exclusively carried out for understanding the amplification pattern occurring in gulfs and ports in the Arabian sea. Tsunami waves entering the ports and gulfs can lead to different amplification patterns. At this juncture, this paper investigates the pattern of amplification occurring along four representative sectors along the west coast namely Gulf of Kutch, Gulf of Khambhat, Mangalore port and Cochin inlet. The simulation results show trivial amplification in Gulf of Kutch and Gulf of Khambhat. The studies of numerical simulation suggest that the amplification factor depends on several other factors like orientation of the coast, coastal geometry of bays and gulfs, near shore bathymetry and depth inside gulfs and ports. How to cite this article: Praveen SS. Numerical Simulation Studies about the Resonance of Tsunami Waves in Selected Gulfs and Ports along the South West Coast of India (SWCI). J Adv Res Appl Mech Compu Fluid Dyna 2020; 4(1): 1-5. DOI: https://doi.org/10.24321/2349.7661.202001

Baseline Assessment of the Importance of Contributions from Regional Seismic Networks to the Pacific Tsunami Warning Center’s Operations

Abstract The Pacific Tsunami Warning Center’s (PTWC’s) core mission consists in saving lives and minimizing property damage through the issuance of timely, effective tsunami warnings and threat messages. For this purpose, the center relies primarily not only on the analysis of near-real-time seismic data streams provided by established networks such as the Global Seismic Network (GSN), but also by an increasing number of stations contributed by regional seismic networks (RSNs) from around the world. We used theoretical computations of the detection time of the first arriving P wave as a proxy to highlight the areas where RSN contributions have the greatest operational impact. To this goal, the P-wave detection times computed for the GSN provided a baseline to isolate the contribution of the RSN in the form of spatially distributed detection time gains. Inspection of the resulting global maps reveals detection time gains of more than 3 m for Hawaii, Alaska, the east and west coasts of the United States, South America, New Zealand, the southwest Pacific, Australia, and the Sunda arc. Despite higher density of GSN baseline stations across the U.S. west coast and the eastern Caribbean, contributions from RSNs result in detection time gains of more than 2 m. These gains in earthquake detection speed correlate well with the continuous increase in the number of stations ingested into the PTWC system and the gradual reduction of the operational median response time to under 6 m from origin during the last 5 yr. These results allow us to conclude that fulfillment of the PTWC’s international and domestic tsunami warning responsibilities critically depends on the support of the RSNs contributing data to PTWC’s daily operations.

Evaluation of Australian Tsunami Warning Thresholds Using Inundation Modelling

Tsunami warnings issued by the Joint Australian Tsunami Warning Centre (JATWC) are derived from a database (T2) consisting of more than two thousand pre-computed tsunami scenarios. Following any potentially tsunamigenic earthquake, warnings are issued for individual coastal zones with three different levels of threat: Land Threat, Marine Threat or No Threat. The decision is based on the 95th percentile (P95) of the maximum wave amplitudes (over time) of the relevant T2 scenario within each coastal zone. Threshold values for P95 have previously been derived through analysis of observed impacts for recent events. Given that historical records are available for only a short time period and no observations exist for which a Land Threat would have been issued for Australia, it has been difficult to determine the appropriate threshold for a Land Threat. Several recent tsunami hazard assessment studies have used inundation models nested within T2 scenarios. These modelling results are used to evaluate the threshold values for JATWC tsunami warnings and provide guidance on a possible further warning tier???Major Land Threat. The optimal Land Threat threshold for P95 is found to be 48.5 cm, however, it is not recommended that any changes are made from the existing operational threshold of 55 cm. The optimal threshold for P95 a Major Land Threat is found to be 150.5 cm.

Impact of hurricanes Irma and Maria on the Pacific Tsunami Warning Center initial tsunami warning capability for the Caribbean region

Abstract. In September 2017, hurricanes Irma and Maria wreaked havoc across the Caribbean region. While obliterating the infrastructure in the Caribbean nations found along their path, both hurricanes gradually destroyed the existing seismic networks. We quantified the impact of the hurricanes on the Pacific Tsunami Warning Center (PTWC) initial tsunami warning capability for the Caribbean region relying on the computation of theoretical earthquake detection and response times after accounting for hurricane-related station outages. The results show that the hurricanes rendered 38 % of the 146 stations available in the Caribbean inoperative. Within the eastern Caribbean region monitored by PTWC the hurricanes exacerbated outages to an astonishing 82 % of the available 76 seismic stations. Puerto Rico, the Virgin Islands, and the Lesser Antilles suffered the brunt of both hurricanes, and their seismic networks nearly disappeared. The double punch delivered by two successive category 5 hurricanes added up to 02:43 and 04:33 min to the earthquake detection and response times, effectively knocking out PTWC's local tsunami warning capabilities in the region. Emergency adjustments, including the temporary reduction of the number of stations required for earthquake detection and ML magnitude release, enabled a faster response to earthquakes in the region than otherwise possible in the aftermath of hurricanes Irma and Maria.

An Evaluation of Modelled Tsunami Arrival Times

The Joint Australian Tsunami Warning Centre provides forecasts of tsunami arrival times based on the Tsunami Travel Times (TTT) software. In this work, travel times from a pre-computed scenario database and TTT are evaluated through comparison with observed arrival times at tide gauges and tsunameters. It is found that travel times from the scenario database are at least as accurate as those from TTT and in most cases, more accurate. The ‘best’ scenario-based method is Tp20—the time of arrival of the first peak that is at least 20% of the maximum amplitude at that point.

Correlation Equation of Fault Size, Moment Magnitude, and Height of Tsunami Case Study: Historical Tsunami Database in Sulawesi

Sulawesi, one of the biggest island in Indonesia, located on the convergence of two macro plate that is Eurasia and Pacific. NOAA and Novosibirsk Tsunami Laboratory show more than 20 tsunami data recorded in Sulawesi since 1820. Based on this data, determination of correlation between tsunami and earthquake parameter need to be done to proved all event in the past. Complete data of magnitudes, fault sizes and tsunami heights on this study sourced from NOAA and Novosibirsk Tsunami database, completed with Pacific Tsunami Warning Center (PTWC) catalog. This study aims to find correlation between moment magnitude, fault size and tsunami height by simple regression. The step of this research are data collecting, processing, and regression analysis. Result shows moment magnitude, fault size and tsunami heights strongly correlated. This analysis is enough to proved the accuracy of historical tsunami database in Sulawesi on NOAA, Novosibirsk Tsunami Laboratory and PTWC.

Evaluation of the Pacific Tsunami Warning Center’s Performance for the Caribbean Based on the Compilation and Analysis of Tsunami Messages Issued between 2003 and July 2017

Evaluation of the Pacific Tsunami Warning Center’s Performance for the Caribbean Based on the Compilation and Analysis of Tsunami Messages Issued between 2003 and July 2017

Assessment of the Pacific Tsunami Warning Center’s Capabilities for Puerto Rico and the Virgin Islands based on the Computation of Detection and Response Times Accounting for Seismic Network Topology and Data Latencies

Assessment of the Pacific Tsunami Warning Center’s Capabilities for Puerto Rico and the Virgin Islands based on the Computation of Detection and Response Times Accounting for Seismic Network Topology and Data Latencies

Coastal Amplification Laws for the French Tsunami Warning Center: Numerical Modeling and Fast Estimate of Tsunami Wave Heights Along the French Riviera

Tsunami modeling tools in the French tsunami Warning Center operational context provide rapidly derived warning levels with a dimensionless variable at basin scale. A new forecast method based on coastal amplification laws has been tested to estimate the tsunami onshore height, with a focus on the French Riviera test-site (Nice area). This fast prediction tool provides a coastal tsunami height distribution, calculated from the numerical simulation of the deep ocean tsunami amplitude and using a transfer function derived from the Green’s law. Due to a lack of tsunami observations in the western Mediterranean basin, coastal amplification parameters are here defined regarding high resolution nested grids simulations. The preliminary results for the Nice test site on the basis of nine historical and synthetic sources show a good agreement with the time-consuming high resolution modeling: the linear approximation is obtained within 1 min in general and provides estimates within a factor of two in amplitude, although the resonance effects in harbors and bays are not reproduced. In Nice harbor especially, variation in tsunami amplitude is something that cannot be really assessed because of the magnitude range and maximum energy azimuth of possible events to account for. However, this method is well suited for a fast first estimate of the coastal tsunami threat forecast.

A Collaborative Effort Between Caribbean States for Tsunami Numerical Modeling: Case Study CaribeWave15

Historical records have shown that tsunami have affected the Caribbean region in the past. However infrequent, recent studies have demonstrated that they pose a latent hazard for countries within this basin. The Hazard Assessment Working Group of the ICG/CARIBE-EWS (Intergovernmental Coordination Group of the Early Warning System for Tsunamis and Other Coastal Threats for the Caribbean Sea and Adjacent Regions) of IOC/UNESCO has a modeling subgroup, which seeks to develop a modeling platform to assess the effects of possible tsunami sources within the basin. The CaribeWave tsunami exercise is carried out annually in the Caribbean region to increase awareness and test tsunami preparedness of countries within the basin. In this study we present results of tsunami inundation using the CaribeWave15 exercise scenario for four selected locations within the Caribbean basin (Colombia, Costa Rica, Panama and Puerto Rico), performed by tsunami modeling researchers from those selected countries. The purpose of this study was to provide the states with additional results for the exercise. The results obtained here were compared to co-seismic deformation and tsunami heights within the basin (energy plots) provided for the exercise to assess the performance of the decision support tools distributed by PTWC (Pacific Tsunami Warning Center), the tsunami service provider for the Caribbean basin. However, comparison of coastal tsunami heights was not possible, due to inconsistencies between the provided fault parameters and the modeling results within the provided exercise products. Still, the modeling performed here allowed to analyze tsunami characteristics at the mentioned states from sources within the North Panama Deformed Belt. The occurrence of a tsunami in the Caribbean may affect several countries because a great variety of them share coastal zones in this basin. Therefore, collaborative efforts similar to the one presented in this study, particularly between neighboring countries, are critical to assess tsunami hazard and increase preparedness within the countries.

THE HELLENIC NATIONAL TSUNAMI WARNING CENTER: RESEARCH, OPERATIONAL AND TRAINING ACTIVITIES

The Hellenic National Tsunami Warning Center (HL-NTWC), which is a unit of the Institute of Geodynamics of the National Observatory of Athens (NOA-IG), was officially established in Greece by law in September 2010. It operates a 24/7 tsunami monitoring service for Greece and the eastern Mediterranean Sea, providing warning messages to the General Secretariat for Civil Protection in Greece. Since August 2012, HL-NTWC acts as Candidate Tsunami Service Provider (CTSP) in the framework of the North-Eastern Atlantic, the Mediterranean and connected seas Tsunami Warning System (NEAMTWS) of the IOC/UNESCO providing tsunami messages to a large number of subscribers. The HL-NTWC function is based on the national seismograph and tide gauge networks of NOA-IG and incorporates several data bases, algorithms and computational tools. Collaboration with top class research institutions in the framework of important EC funded tsunami research projects strengthens the scientific background of the center. Tests, exercises and training of the duty officers involved in the 24/7 operation of the HL-NTWC are carried on constantly, in order to maintain a high level of readiness and response in case of emergency. In its operational life since August 2012 the HL-NTWC has timely issued tsunami warning messages for 14 potentially tsunamigenic earthquake events.

Tsunami hazard in Central America: history and future

Abstract Central America is a small and culturally homogeneous region that, since the 1990s, has experienced economic and political integration of its six countries, which share the same threats of volcanic eruptions, disastrous earthquakes and tsunamis. The Pacific coastline of 1700 km is common for Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica and Panama, and the Pacific subduction zone has the potential for creating huge tsunamis that threaten this coast. In addition to the natural hazard, the growing tourist industry is expanding its infrastructure along the Pacific beaches, which again enhances the exposure and tsunami risk. Even though the 1992 tsunami disaster in Nicaragua did not severely hit the tourist beaches, it raised the risk awareness, and special attention is now given to ‘slow’ earthquakes that may be modest in shaking while still having a large tsunami potential. The tsunami hazard mapping is well advanced in Nicaragua, Costa Rica and El Salvador, and initiatives are ongoing to improve the mapping in all countries. National systems for early warning were established in Nicaragua and El Salvador, while the other four countries rely on rapid information from the Pacific Tsunami Warning Center. Mitigation measures and information campaigns are presently conducted on a national basis in all countries, but a regional centre for early tsunami warning and coordinated information campaigns (CATAC) is expected to become operational in the near future.

A Pilot Tsunami Inundation Forecast System for Australia

The Joint Australian Tsunami Warning Centre (JATWC) provides a tsunami warning service for Australia. Warnings are currently issued according to a technique that does not include explicit modelling at the coastline, including any potential coastal inundation. This paper investigates the feasibility of developing and implementing tsunami inundation modelling as part of the JATWC warning system. An inundation model was developed for a site in Southeast Australia, on the basis of the availability of bathymetric and topographic data and observations of past tsunamis. The model was forced using data from T2, the operational deep-water tsunami scenario database currently used for generating warnings. The model was evaluated not only for its accuracy but also for its computational speed, particularly with respect to operational applications. Limitations of the proposed forecast processes in the Australian context and areas requiring future improvement are discussed.