Tsunami Detection Research Articles

Cost-Effective, Cognitive Undersea Network for Timely and Reliable Near-Field Tsunami Warning

The focus of this paper is on developing an early detection and warning system for near-field tsunami to mitigate its impact on communities at risk. This a challenging task, given the stringent reliability and timeliness requirements, the development of such an infrastructure entails. To address this challenge, we propose a hybrid infrastructure, which combines cheap but unreliable undersea sensors with expensive but highly reliable fiber optic, to meet the stringent constraints of this warning system. The derivation of a low-cost tsunami detection and warning infrastructure is cast as an optimization problem, and a heuristic approach is used to determine the minimum cost network configuration that meets the targeted reliability and timeliness requirements. To capture the intrinsic properties of the environment and model accurately the main characteristics of the sound wave propagation undersea, the proposed optimization framework incorporates the Bellhop propagation model and accounts for significant environment factors, including noise, varying undersea sound speed and sea floor profile. We apply our approach to a region which is prone to near-field tsunami threats to derive a cost-effective under sea infrastructure for detection and warning. For this case study, the results derived from the proposed framework show that a feasible infrastructure, which operates with a carrier frequency of 12-KHz, can be deployed in calm, moderate and severe environments and meet the stringent reliability and timeliness constraints, namely 20 minutes warning time and 99 % data communication reliability, required to mitigate the impact of a near-field tsunami. The proposed framework provides useful insights and guidelines toward the development of a realistic detection and warning system for near-field tsunami.

Elders Recall an Earlier Tsunami on Indian Ocean Shores

Ten years later, the Indian Ocean tsunami of 26 December 2004 still looms large in efforts to reduce tsunami risk. The disaster has spurred worldwide advances in tsunami detection and warning, risk assessment, and awareness [Satake, 2014].

FIELD INVESTIGATION OF LONG-TERM MOORING CHAIN SYSTEM DURABILITY OF THE GPS TSUNAMI-WAVE METER

This paper aims for providing basic information of the mooring design of the GPS mounted Tsunami-Wave meter buoy, which successfully observed exact offshore tsunami profile of the 2011 off the Pacific coast of Tohoku Earthquake. Deep-sea sensors can detect tsunami profiles minutes before its arrival on the coast. That is very important to prevent and/or reduce tsunami disasters (Nagai, et.al., 2006). But as tsunamis are very rare events for human life scale, it is difficult for human societies to keep the offshore tsunami monitoring system in good condition for long years, if the system is applicable only for tsunami detection. Real-time offshore tsunami detection system should be well maintained only if the system provides us routine useful sea information like waves and swells. Routine multi-purpose usefulness of the observed data may make the system more cost effective than only be applicable for very rare and immediate tsunami monitoring (Nagai, et.al., 2007). Existing deep-sea seabed installed pressure gauge is applicable only to tsunami event, for deep-sea wave and swell actions do not reach the seabed. That is why offshore GPS buoy system is the only one technique that has succeeded to serve authorized real-time tsunami warning before its arrival to the coast line at the 2011 off the Pacific coast of Tohoku Earthquake tsunami event in Japan. In this paper, authors introduce observation data of proto-type GPS buoy's mooring chain at 3 years and 7 months after the installation in the severe sea condition, in order to provide information for practical design of future safer and more economical design of the mooring system.

Tsunami observations in the open ocean

Deep-sea tsunami measurements play a major role in understanding the physics of tsunami wave generation and propagation, and in the creation of an effective tsunami warning system. The paper provides an overview of the history of tsunami recording in the open ocean from the beginning (about 50 years ago) to the present day. It describes modern tsunami monitoring systems, including the Deep-ocean Assessment and Reporting of Tsunamis (DART), innovative Japanese bottom cable projects, and the NEPTUNE-Canada geophysical bottom observatory. The specific peculiarities of seafloor longwave observations in the deep ocean are discussed and compared with those recorded in coastal regions. Tsunami detection in bottom presure observations is exemplified based on analysis of distant (22000 km) records of the 2004 Sumatra tsunami in the northeastern Pacific.

Measuring Ocean Bottom Pressure at the North Pole

AbstractHigh-precision deep Arctic Bottom Pressure Recorders (ABPRs) were developed to measure ocean bottom pressure variations in the perennial ice-covered Arctic Ocean. The ABPRs use the tsunami detection DART acoustic modem technology and have been programmed to store and transmit the data acoustically without the need to recover the instrument. ABPRs have been deployed near the North Pole, where the ice cover is a year-round challenge for access with a ship. Instead, the ABPRs have been built as light-weight mechanical systems that we can install using aircraft landing on the ice. ABPRs have provided the first records of uninterrupted pressure data over continuous years ever made in the central Arctic. The ABPR data have allowed us to identify and understand modes of Arctic Ocean bottom pressure variability that were unknown before the ABPR records and have offered new means of investigating and understanding the rapidly changing Arctic system. The ABPR records have also shown outstanding agreement with the satellite-sensed ocean bottom pressure anomalies from GRACE, providing ground truth data for validation of the satellite system. Due to the successful science findings as well as the ABPRs' capability to fulfill the upcoming potential gaps of pressure measurements between GRACE and a GRACE follow-on mission, we highlight the urgent need to develop and maintain an Arctic observing network using ABPRs.

Overlapping sea level time series measured using different technologies: an example from the REDMAR Spanish network

Abstract. This paper addresses the problems of overlapping sea level time series measured using different technologies and sometimes from different locations inside a harbour. The renovation of the Spanish REDMAR (RED de MAReógrafos) sea level network is taken here as an example of the difficulties encountered: up to seventeen old tide gauge stations have been replaced by radar tide gauges all around the Spanish coast, in order to fulfil the new international requirements on tsunami detection. Overlapping periods between old and new stations have allowed the comparison of records in different frequency ranges and the determination of the impact of this change of instrumentation on the long-term sea level products such as tides, surges and mean sea levels. The differences encountered are generally within the values expected, taking into account the characteristics of the different sensors, the different sampling strategies and sometimes the different locations inside the harbours. However, our analysis has also revealed in some cases the presence of significant scale errors that, overlapping with datum differences and uncertainties, as well as with hardware problems in many new radar gauges, may hinder the generation of coherent and continuous sea level time series. Comparisons with nearby stations have been combined with comparisons with altimetry time series close to each station in order to better determine the sources of error and to guarantee the precise relationships between the sea level time series from the old and the new tide gauges.

A Study of the Algorithms for the Detection of Tsunami Using an Ocean Bottom Pressure Recorder

AbstractThe National Institute of Ocean Technology (NIOT), an autonomous organization under the Ministry of Earth Sciences, government of India, is engaged in developing and installing systems for tsunami detection and reporting. This involves high-precision bottom pressure recorders (BPRs) installed on the ocean floor, which can detect water level changes in the order of a few centimeters. Data are logged and recorded subsea by instruments located close to the BPRs. The detection of abnormal changes in the water level is required for detecting a tsunami event. This paper describes algorithms incorporated in most BPRs for detecting a tsunami by predictive methods such as Newton’s Extrapolation and Kalman predictor techniques. The most widely used tsunami detection algorithm is based on Newton’s extrapolation. The tsunami detection technique based on the Kalman prediction algorithm developed by NIOT can be an alternative for the existing technique. This paper describes both the algorithms and analyzes their effectiveness during tsunami event detection using MATLAB software. It is found that the Kalman algorithm has a better detection performance over the Newton extrapolation technique for tsunami wave amplitudes up to 300 mm. The Newton extrapolation technique has a better detection performance for tsunami wave duration of less than 10 min. For tsunami wave durations greater than 10 min, the Kalman algorithm has a better detection performance. As the wave durations of most of the recorded tsunamis are greater than 10 min, the Kalman algorithm could be a viable substitute for tsunami detection.

High frequency radar applications in coastal monitoring, planning and engineering

This paper reviews some existing and potential applications of high frequency (HF) radar surface current, wave and wind data drawing on experiences within Australia and also from elsewhere in the world. These include oil spill transport, search and rescue services, navigational safety, marine renewables, tsunami detection, water quality and coastal development projects, and many different applications in the area of marine ecology. The data are also used for studies of ocean dynamics and for the validation of hydrodynamic and wave models. Some new wind direction and wave measurements from the Australian radar systems are presented. The quality of the data is crucial to all these applications and some examples of data validation are discussed. Learning from the experiences of other more developed networks, and in particular building solid links with the user communities in Australia, is essential to ensure long-term sustainability of the Australian HF radar network.

Algorithms for Automatic, Real-time Tsunami Detection in Wind-wave Measurements: Using Strategies and Practical Aspects

The present paper concentrates on the actual use - in the framework of a Tsunami Early Warning System - of the algorithms to be implemented in the software of wind-wave gages in order to automatically perform the real-time detection of tsunamis within recorded signals. Focus is on the amplitude-discriminating algorithm, mainly based on an infinite impulse response time domain filter, proposed by the authors in a previous paper. In particular, the problems that may arise in filtering out ‘disturbances’ such as long tidal waves are addressed, and an original method to perform the full characterization of the waveform of an actually detected tsunami, automatically and in ‘quasi’ real-time is proposed. Tests were carried out using time-series resulting from the superposi- tion of actual tsunami signals recorded by some of the tsunamometers of the Deep-ocean Assessment and Reporting of Tsunamis program, and different wind-wave signals synthesized by means of the random-phase method. In particular, the tsunamometers’ records collected during the events triggered by the earthquakes occurred off the coast of Chile on February 27, 2010, and off the Pacific Coast of Tohoku (Japan) on March 11, 2011, were used. The results show that the overall detection and characterization of a tsunami can be effectively carried out, automatically and in real-time, using the proposed new algorithm.

Internet of Things (IoT): Present State and Future Prospects

SUMMARY The recent development of communication devices and wireless network technologies continues to advance the new era of the Internet and telecommunications. The various “things”, which include not only communication devices but also every other physical object on the planet, are also going to be connected to the Internet, and controlled through wireless networks. This concept, which is referred to as the “Internet of Things (IoT)”, has attracted much attention from many researchers in recent years. The concept of IoT can be associated with multiple research areas such as body area networks, Device-to-Device (D2D) communications networks, home area networks, Unmanned Aerial Vehicle (UAV) networks, satellite networks, and so forth. Also, there are various kinds of applications created by using IoT technologies. Thus, the concept of the IoT is expected to be integrated into our society and support our daily life in the near future. In this paper, we introduce different classifications of IoT with examples of utilizing IoT technologies. In addition, as an example of a practical system using IoT, a tsunami detection system (which is composed of a satellite, sensor terminals, and an active monitoring system for real-time simultaneous utilization of the devices) is introduced. Furthermore, the requirements of the next generation systems with the IoT are delineated in the paper.

Calibration of a real-time tsunami detection algorithm for sites with no instrumental tsunami records: application to coastal tide-gauge stations in eastern Sicily, Italy

Abstract. Coastal tide gauges play a very important role in a tsunami warning system, since sea-level data are needed for a correct evaluation of the tsunami threat, and the tsunami arrival has to be recognized as early as possible. Real-time tsunami detection algorithms serve this purpose. For an efficient detection, they have to be calibrated and adapted to the specific local characteristics of the site where they are installed, which is easily done when the station has recorded a sufficiently large number of tsunamis. In this case the recorded database can be used to select the best set of parameters enhancing the discrimination power of the algorithm and minimizing the detection time. This chance is however rare, since most of the coastal tide-gauge stations, either historical or of new installation, have recorded only a few tsunamis in their lifetimes, if any. In this case calibration must be carried out by using synthetic tsunami signals, which poses the problem of how to generate them and how to use them. This paper investigates this issue and proposes a calibration approach by using as an example a specific case, which is the calibration of a real-time detection algorithm called TEDA (Tsunami Early Detection Algorithm) for two stations (namely Tremestieri and Catania) in eastern Sicily, Italy, which were recently installed in the frame of the Italian project TSUNET, aiming at improving the tsunami monitoring capacity in a region that is one of the most hazardous tsunami areas of Italy and of the Mediterranean.

Impact of Near-Field, Deep-Ocean Tsunami Observations on Forecasting the 7 December 2012 Japanese Tsunami

Following the devastating 11 March 2011 tsunami, two deep-ocean assessment and reporting of tsunamis (DART®)(DART® and the DART® logo are registered trademarks of the National Oceanic and Atmospheric Administration, used with permission) stations were deployed in Japanese waters by the Japanese Meteorological Agency. Two weeks after deployment, on 7 December 2012, a M w 7.3 earthquake off Japan’s Pacific coastline generated a tsunami. The tsunami was recorded at the two Japanese DARTs as early as 11 min after the earthquake origin time, which set a record as the fastest tsunami detecting time at a DART station. These data, along with those recorded at other DARTs, were used to derive a tsunami source using the National Oceanic and Atmospheric Administration tsunami forecast system. The results of our analysis show that data provided by the two near-field Japanese DARTs can not only improve the forecast speed but also the forecast accuracy at the Japanese tide gauge stations. This study provides important guidelines for early detection and forecasting of local tsunamis.

Data acquisition and processing at ocean bottom for a Tsunami warning system

The design and development of a Bottom Pressure Recorder for a Tsunami Early Warning System is described here. The special requirements that it should satisfy for the specific application of deployment at ocean bed and pressure monitoring of the water column above are dealt with. A high-resolution data digitization and low circuit power consumption are typical ones. The implementation details of the data sensing and acquisition part to meet these are also brought out. The data processing part typically encompasses a Tsunami detection algorithm that should detect an event of significance in the background of a variety of periodic and aperiodic noise signals. Such an algorithm and its simulation are presented. Further, the results of sea trials carried out on the system off the Chennai coast are presented. The high quality and fidelity of the data prove that the system design is robust despite its low cost and with suitable augmentations, is ready for a full-fledged deployment at ocean bed.

Tsunami and acoustic-gravity waves in water of constant depth

A study of wave radiation by a rather general bottom displacement, in a compressible ocean of otherwise constant depth, is carried out within the framework of a three-dimensional linear theory. Simple analytic expressions for the flow field, at large distance from the disturbance, are derived. Realistic numerical examples indicate that the Acoustic-Gravity waves, which significantly precede the Tsunami, are expected to leave a measurable signature on bottom-pressure records that should be considered for early detection of Tsunami.

Use of tide gauge data in operational oceanography and sea level hazard warning systems

International recommendations to upgrade sea level networks all around the globe have led to sea level data now being available at different international and national data centres and portals, with a variety of latencies and data sampling, and not always adequately quality controlled. This paper describes several automatic algorithms that allow the quality control, processing and more reliable use and interpretation of these tide gauge data. These algorithms, originally implemented at Puertos del Estado for the REDMAR Spanish network, include near-real time processing for operational model validation and tsunami detection algorithms. Some elements of this software were implemented or extended to other tide gauges in Europe within the framework of different European projects.

From Sumatra 2004 to Tohoku‐Oki 2011: The systematic GPS detection of the ionospheric signature induced by tsunamigenic earthquakes

The recent tsunamigenic earthquake in Tohoku (11 March 2011) strongly affirms, one more time after the Sumatra event (26 December 2004), the necessity to open new paradigms in oceanic monitoring. Detection of ionospheric anomalies following the Sumatra tsunami demonstrated that ionosphere is sensitive to the tsunami propagation. Observations supported by modeling proved that tsunamigenic ionospheric anomalies are deterministic and reproducible by numerical modeling via the ocean/neutral‐atmosphere/ionosphere coupling mechanism. In essence, tsunami induces internal gravity waves propagating within the neutral atmosphere and detectable in the ionosphere. Most of the ionospheric anomalies produced by tsunamis were observed in the far field where the tsunami signature in the ionosphere is clearly identifiable. In this work, we highlight the early signature in the ionosphere produced by tsunamigenic earthquakes and observed by GPS, measuring the total electron content, close to the epicenter. We focus on the first hour after the seismic rupture. We demonstrate that acoustic‐gravity waves generated at the epicenter by the direct vertical displacement of the source rupture and the gravity wave coupled with the tsunami can be discriminated with theoretical support. We illustrate the systematic nature of those perturbations showing several observations: nominally the ionospheric perturbation following the tsunamigenic earthquakes in Sumatra on 26 December 2004 and 12 September 2007; in Chile on 14 November 2007; in Samoa on 29 September 2009; and the recent catastrophic Tohoku‐Oki event on 11 March 2011. Based on the analytical description, we provide tracks for further modeling efforts and clues for the interpretation of complex—and thus often misleading—observations. The routine detection of the early ionospheric anomalies following the rupture highlights the role of ionospheric sounding in the future ocean monitoring and tsunami detection.

Analysis and modelling of tsunami-induced tilt for the 2007, M = 7.6, Tocopilla and the 2010, M = 8.8 Maule earthquakes, Chile, from long-base tiltmeter and broadband seismometer records

We present a detailed study of tsunami-induced tilt at in-land sites, to test the interest and feasibility of such analysis for tsunami detection and modelling. We studied tiltmeter and broadband seismometer records of northern Chile, detecting a clear signature of the tsunamis generated by the 2007 Tocopilla (M = 7.6) and the 2010 Maule (M = 8.8) earthquakes. We find that these records are dominated by the tilt due to the elastic loading of the oceanic floor, with a small effect of the horizontal gravitational attraction. We modelled the Maule tsunami using the seismic source model proposed by Delouis et al. and a bathymetric map, correctly fitting three tide gauge records of the area (Antofagasta, Iquique and Arica). At all the closest stations (7 STS2, 2 long-base tiltmeters), we correctly modelled the first few hours of the tilt signal for the Maule tsunami. The only phase mismatch is for the site that is closer to the ocean. We find a tilt response of 0.005–0.01 μm at 7 km away from the coastline in response to a sea level amplitude change of 10 cm. For the Maule earthquake, we observe a clear tilt signal starting 20 min before the arrival time of the tsunami at the nearest point on the coastline. This capability of tilt or seismic sensors to detect distant tsunamis before they arrive has been successfully tested with a scenario megathrust in the southern Peru-northern Chile seismic gap. However, for large events near the stations, this analysis may no longer be feasible, due to the large amplitude of the long-period seismic signals expected to obscure the loading signal. Inland tilt measurements of tsunamis smooth out short, often unmodelled wavelengths of the sea level perturbation, thus providing robust, large-scale images of the tsunami. Furthermore, tilt measurements are not expected to saturate even for the largest run-ups, nor to suffer from near-coast tsunami damages. Tiltmeters and broadband seismometers are thus valuable instruments for monitoring tsunamis in complement with tide gauge arrays.

Near-field tsunami early warning and emergency planning in the Mediterranean Sea

The new European project <em>Near-field Tsunami Early Warning and Emergency Planning in the Mediterranean Sea</em> (NEARTOWARN) faces the need to develop operational tsunami early warning systems in near-field (local) conditions where the travel time of the first tsunami wave is very short, that is less than 30 min, which is a typical case in the North East Atlantic and the Mediterranean Sea region but also elsewhere around the globe. The operational condition that should be fulfilled is that the time of tsunami detection, plus the time of warning transmitting, plus the time of evacuation should not exceed the travel time of the first tsunami wave from its source to the closest evacuation zone. To this goal the time to detect of the causative earthquake should be compressed at the very minimum. In this context the core of the proposed system is a network of seismic early warning devices, which activate and send alert in a few seconds after the generation of a near-field earthquake, when a seismic ground motion exceeding a prescribed threshold is detected. Then civil protection mobilizes to manage the earthquake crisis but also to detect and manage a possible tsunami through a geographical risk management system. For the tsunami detection the system is supported by tide-gauges of radar type, a database of presimulated tsunami scenarios, and a local tsunami decision matrix. The island of Rhodes in the eastern termination of the Hellenic Arc and Trench has been selected for a pilot and operational development of the local tsunami warning system given that the island is a highly popular tourist destination, historically it was hit by large tsunamigenic earthquakes and was recently the master test-site for the pan-European FP6 tsunami research project <em>Tsunami Risk ANd Strategies For the European Region</em> (TRANSFER).

Progressive waves in a compressible-ocean with an elastic bottom

The mathematical solution for the two-dimensional linear problem of acoustic-gravity waves in a compressible ocean with an elastic bottom is presented. The physical properties of these waves are studied, and compared with those for waves over rigid ground. The solutions for constant water depth, together with the assumption of constant energy flux, are used to study the shoaling of acoustic-gravity waves over a slowly-varying bathymetry. The present work enriches our knowledge about acoustic-gravity waves in a way that could assist, among others, in the early detection of tsunami.

Development of oceanographic radar networks, data management and applications in Asia and Oceania countries

Oceanographic radar systems are unique in providing near real-time two dimensional maps of densely distributed (0.3~6 km grid) surface currents and wave characteristics over a large region of the coastal ocean extending about 200 km from the shoreline, and can operate under any weather conditions. Oceanographic radars are extremely valuable for marine ecological, economic, and safety applications; ship navigation, oil spill prediction, search and rescue, harmful algal bloom forecasting and tsunami detection and warning, as well as coastal sea surface circulation studies and forecast. Demands for densely sampled near real-time surface current data have increased in Asian countries with increasing maritime transportation, fishery activities, coastal zone usages and pollutions, and ocean leisure activities. However, data production from the radar requires high tech engineering because the radio-wave environment, operational skill and maintenance of the radar system and data management may affect data quality and quantity. Despite more than 110 oceanographic radars are presently operating in Asia and Oceania country’s coast line, there have been few oceanographic radar conferences among the Asian radar communities to address frequency sharing, operation and maintenance, data verification and gap filling as well as the results of research and application.