Tsunami Buoy Research Articles

Comparison of Earthquake Source Models for the 2011 Tohoku Event Using Tsunami Simulations and Near-Field Observations

Selection of the earthquake source used in tsunami models of the 2011 Tohoku event affects the simulated tsunami waveform across the near field. Different earthquake sources, based on inversions of seismic waveforms, tsunami waveforms, and Global Positioning System (GPS) data, give distinguishable patterns of simulated tsunami heights in many locations in Tohoku and at near‐field Deep‐ocean Assessment and Reporting of Tsunamis (DART) buoys. We compared 10 sources proposed by different research groups using the GeoClaw code to simulate the resulting tsunami. Several simulations accurately reproduced observations at simulation sites with high grid resolution. Many earthquake sources produced results within 20% difference from the observations between 38° and 39° N, including realistic inundation on the Sendai plain, reflecting a common reliance on large initial seafloor uplift around 38° N (±0.5°), 143.25° E (±0.75°). As might be expected, DART data was better reproduced by sources created by inversion techniques that incorporated DART data in the inversion. Most of the earthquake sources tested at sites with high grid resolution were unable to reproduce the magnitude of runup north of 39° N, indicating that an additional source of tsunamigenic energy, not present in most source models, is needed to explain these observations. Online Material: Figures of buoy, inundation and run‐up simulations and observations, associated data sets, and simulation code.

The role of tsunami buoy played in tsunami warning and its application in South China Sea

The tsunami was a sudden marine disasters. Tsunami waves can quickly spread to near-shore and cause the disaster after the tsunami. So it is very important of timely monitoring and early warning of the tsunami. After several unsuccessful tsunami forecasting, the United States developed tsunami buoy specifically for the early detection of tsunami waves. Tsunami buoy can not only be able to display occurrence of the tsunami, it is real time data but also be assimilated into the tsunami warning system, to improve the accuracy of the tsunami forecasting. Several tsunami events in the recent few years have proven the important role of the tsunami buoys. Subsequently, the tsunami warning system based on tsunami buoys was into regular operation. The system accurately predicted the results on March 11, 2011 Japan tsunami event. State Oceanic Administration (SOA), China also deployed 2 tsunami buoys in the South China Sea (SCS), which also played an important role in the warning process of Japan tsunami on March 11, 2011. National Marine Environmental Forecasting Center/State Oceanic Administration (NMEFC/SOA) will collaborate with Pacific Marine Environmental Laboratory/National Oceanic and Atmospheric Administration (PMEL/NOAA) to develop assimilation method making use of real time data of tsunami buoy and build a forecasting system in SCS in the future.

Modeling Propagation of 2011 Honshu Tsunami

In this study, the Honshu tsunami on 11 March 2011 was simulated using the Regional Ocean Model System (ROMS) governed by two - dimensional nonlinear shallow - water equations and driven by three earthquake deformation fields as initial condition. The purpose of this study is to assess the model’s sensitivity to the tsunami source field, especially the case in which the horizontal deformation of earthquake was taken into account. The comparison between the model results and observed tsunami waves at 14 Deep-ocean Assessment and Reporting of Tsunami (DART) buoy stations showed that the average errors of modeled maximum wave amplitude were 23.2%, 26.9% and 37.4% for the three initial deformation fields, respectively. In the best performance case, when the observed wave amplitude was below 0.3 m, the average error of the modeled maximum wave amplitude was 0.034 m and relative error was 23.7%. On the other hand, the average errors of modeled arrival times of the first tsunami - wave peak at 13 DART stations were 2.82, 2.28 and 3.48 min earlier for the three cases of different initial fields, but the error is as big as ~3 hrs at Station 46412 located near the west coast of the USA. The model did not resolve the observed wave at Station 46412, which might be caused by the model’s coarse grid that cannot represent the bottom topography well, especially that near the shoreline. The two - dimensional (2D) model employing shallow - water equations could also be a limiting factor. In Case 4 based on the best performance case with horizontally generated wave, the average relative error of maximum wave amplitude was reduced from 23.2% to 20.6% and the root mean square error (RMSE) was reduced from 0.029 m to 0.014 m. The results suggest that the consideration of horizontal deformation of earthquake, which plays an important role in generating tsunami, can help to improve the performance of simulating tsunami wave.

Comparison of the seafloor displacement from uniform and non-uniform slip models on tsunami simulation of the 2011 Tohoku–Oki earthquake

The numerical simulations of recent tsunami caused by 11 March 2011 off-shore Pacific coast of Tohoku–Oki earthquake (Mw 9.0) using diverse co-seismic source models have been performed. Co-seismic source models proposed by various observational agencies and scholars are further used to elucidate the effects of uniform and non-uniform slip models on tsunami generation and propagation stages. Non-linear shallow water equations are solved with a finite difference scheme, using a computational grid with different cell sizes over GEBCO30 bathymetry data. Overall results obtained and reported by various tsunami simulation models are compared together with the available real-time kinematic global positioning system (RTK-GPS) buoys, cabled deep ocean-bottom pressure gauges (OBPG), and Deep-ocean Assessment and Reporting of Tsunami (DART) buoys. The purpose of this study is to provide a brief overview of major differences between point-source and finite-fault methodologies on generation and simulation of tsunamis. Tests of the assumptions of uniform and non-uniform slip models designate that the average uniform slip models may be used for the tsunami simulations off-shore, and far from the source region. Nevertheless, the heterogeneities of the slip distribution within the fault plane are substantial for the wave amplitude in the near field which should be investigated further.

Tsunami source area of the 2011 off the Pacific coast of Tohoku Earthquake determined from tsunami arrival times at offshore observation stations

The source area of the tsunami generated by the 2011 off the Pacific coast of Tohoku Earthquake estimated from tsunami arrival times recorded at offshore wave gauges, GPS buoys, cabled ocean-bottom pressure gauges, and tsunami buoys is about 500-km long with a maximum width of approximately 200 km. The 2011 tsunami source area includes several segments of previous recurring large earthquakes. However, the northern and southern parts of the large Japan Trench segment were not included in the source area. The southern off-Boso-Peninsula part of the Japan Trench segment has the potential to generate a large tsunami earthquake in near future.

GPS water level measurements for Indonesia's Tsunami Early Warning System

Abstract. On Boxing Day 2004, a severe tsunami was generated by a strong earthquake in Northern Sumatra causing a large number of casualties. At this time, neither an offshore buoy network was in place to measure tsunami waves, nor a system to disseminate tsunami warnings to local governmental entities. Since then, buoys have been developed by Indonesia and Germany, complemented by NOAA's Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys, and have been moored offshore Sumatra and Java. The suite of sensors for offshore tsunami detection in Indonesia has been advanced by adding GPS technology for water level measurements. The usage of GPS buoys in tsunami warning systems is a relatively new approach. The concept of the German Indonesian Tsunami Early Warning System (GITEWS) (Rudloff et al., 2009) combines GPS technology and ocean bottom pressure (OBP) measurements. Especially for near-field installations where the seismic noise may deteriorate the OBP data, GPS-derived sea level heights provide additional information. The GPS buoy technology is precise enough to detect medium to large tsunamis of amplitudes larger than 10 cm. The analysis presented here suggests that for about 68% of the time, tsunamis larger than 5 cm may be detectable.

Extraction of tsunami source coefficients via inversion of DART $$^{\circledR}$$ buoy data

The ability to accurately forecast potential hazards posed to coastal communities by tsunamis generated seismically in both the near and far field requires knowledge of so-called source coefficients, from which the strength of a tsunami can be deduced. Seismic information alone can be used to set the source coefficients, but the values so derived reflect the dynamics of movement at or below the seabed and hence might not accurately describe how this motion is manifested in the overlaying water column. We describe here a method for refining source coefficient estimates based on seismic information by making use of data from Deep-ocean Assessment and Reporting of Tsunamis (DART $$^{\circledR}$$ ) buoys (tsunameters). The method involves using these data to adjust precomputed models via an inversion algorithm so that residuals between the adjusted models and the DART $$^{\circledR}$$ data are as small as possible in a least squares sense. The inversion algorithm is statistically based and hence has the ability to assess uncertainty in the estimated source coefficients. We describe this inversion algorithm in detail and apply it to the November 2006 Kuril Islands event as a case study.

EOF analysis of a time series with application to tsunami detection

Abstract Fragments of deep-ocean tidal records up to 3 days long belong to the same functional sub-space, regardless of the record’s origin. The tidal sub-space basis can be derived via Empirical Orthogonal Function (EOF) analysis of a tidal record of a single buoy. Decomposition of a tsunami buoy record in a functional space of tidal EOFs presents an efficient tool for a short-term tidal forecast, as well as for an accurate tidal removal needed for early tsunami detection and quantification [Tolkova, E., 2009. Principal component analysis of tsunami buoy record: tide prediction and removal. Dyn. Atmos. Oceans 46 (1–4), 62–82] EOF analysis of a time series, however, assumes that the time series represents a stationary (in the weak sense) process. In the present work, a modification of one-dimensional EOF formalism not restricted to stationary processes is introduced. With this modification, the EOF-based de-tiding/forecasting technique can be interpreted in terms of a signal passage through a filter bank, which is unique for the sub-space spanned by the EOFs. This interpretation helps to identify a harmonic content of a continuous process whose fragments are decomposed by given EOFs. In particular, seven EOFs and a constant function are proved to decompose 1-day-long tidal fragments at any location. Filtering by projection into a reduced sub-space of the above EOFs is capable of isolating a tsunami wave within a few millimeter accuracy from the first minutes of the tsunami appearance on a tsunami buoy record, and is reliable in the presence of data gaps. EOFs with ∼ 3-day duration (a reciprocal of either tidal band width) allow short-term (24.75 h in advance) tidal predictions using the inherent structure of a tidal signal. The predictions do not require any a priori knowledge of tidal processes at a particular location, except for recent 49.5 h long recordings at the location.

Review of Recent Tsunami Observation by Offshore Cabled Observatory

This paper discusses near- and far-field tsunami observations at the Hokkaido, Japan, offshore cabled observatory, focusing on the 2006 Kuril Island earthquake (Mw 8.3) as a far-field event and the 2008 off-Tokachi earthquake (Mw 6.8) as a near-field event. The Kuril Islands earthquake was detected as a series of tsunami signals by 2 bottom pressure gauges roughly 1 hour after the earthquake. Tsunami amplitudes observed offshore were 3 cm and off-coastal amplitudes were a few tens of centimeters. In the 2008 near-field off-Tokachi earthquake (Mw 6.8), a tsunami signal was detected simultaneously with the earthquake, which had a source amplitude of 4 cm. Our tsunami calculation reproduced the first wave well, but discrepancies about arrival time and amplitude arose for the second and later waves. Offshore tsunami sensors such as bottom pressure gauges, deep-ocean assessment and reporting of tsunami (DART) buoys, and kinematic global positioning system (GPS) buoys may thus become keys in early tsunami warning once appropriate dataset processing is implemented.

EOF analysis of a time series with application to tsunami detection

Fragments of deep-ocean tidal records up to 3 days long belong to the same functional sub-space, regardless of the record’s origin. The tidal sub-space basis can be derived via Empirical Orthogonal Function (EOF) analysis of a tidal record of a single buoy. Decomposition of a tsunami buoy record in a functional space of tidal EOFs presents an efficient tool for a short-term tidal forecast, as well as for an accurate tidal removal needed for early tsunami detection and quantification [Tolkova, E., 2009. Principal component analysis of tsunami buoy record: tide prediction and removal. Dyn. Atmos. Oceans 46 (1–4), 62–82] EOF analysis of a time series, however, assumes that the time series represents a stationary (in the weak sense) process. In the present work, a modification of one-dimensional EOF formalism not restricted to stationary processes is introduced. With this modification, the EOF-based de-tiding/forecasting technique can be interpreted in terms of a signal passage through a filter bank, which is unique for the sub-space spanned by the EOFs. This interpretation helps to identify a harmonic content of a continuous process whose fragments are decomposed by given EOFs. In particular, seven EOFs and a constant function are proved to decompose 1-day-long tidal fragments at any location. Filtering by projection into a reduced sub-space of the above EOFs is capable of isolating a tsunami wave within a few millimeter accuracy from the first minutes of the tsunami appearance on a tsunami buoy record, and is reliable in the presence of data gaps. EOFs with ∼ 3-day duration (a reciprocal of either tidal band width) allow short-term (24.75 h in advance) tidal predictions using the inherent structure of a tidal signal. The predictions do not require any a priori knowledge of tidal processes at a particular location, except for recent 49.5 h long recordings at the location.

Principal component analysis of tsunami buoy record: Tide prediction and removal

Principal component or Empirical Orthogonal Function (EOF) analysis is applied to tsunameter records by treating them as two-dimensional signals, where the second dimension is created by breaking a single time series into cycles and treating the cycle number as a second dimension. Under certain conditions, principal components calculated from different records are shown to determine the same functional space. Signal decomposition into pre-calculated principal components is used to predict or extract the tidal component of a record. This work shows that EOF processing allows for short-term tidal predictions at tsunami buoy locations with the precision of more advanced methods and with minimal a priori knowledge about tidal dynamics. Also shown is that filtering in EOF domain is sensitive to the non-tidal component of a record and therefore presents a tool for early tsunami detection and quantification.

A review of the ocean science and technology partnership between US and Korea

Abstract In 2001, the National Oceanic and Atmospheric Administration (NOAA) and the Ministry of Maritime Affairs and Fisheries Integrated Coastal and Ocean Resources Scientific and Technical Arrangement was signed to pursue scientific and technical cooperation in integrated coastal and ocean resources management in the mutual interest of the participants. Over the last 6 years, the cooperation has been very beneficial, particularly for advancing marine science and management programs in Korea, such as Deep Sea Aquaculture, Sea Grant College Program, Marine Protected Areas, and Ocean Observations. The benefits to NOAA from the cooperation include Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys, ocean and coastal observations, GEOSS program, and Global Program of Action. Also the cooperation has spillover effects on other ocean science and technological arrangement between US and Korea. This article reviews purpose, obstacles, and achievement of the cooperation and suggests recommendations for the future steps.

Indian Ocean tsunami detection buoy deployed

The U.S. National Oceanic and Atmospheric Administration has deployed the first of two Deep‐ocean Assessment and Reporting of Tsunami (DART) buoys in the Indian Ocean.This first buoy was placed about halfway between Thailand and Sri Lanka at the beginning of December 2006 and will be maintained by the Thai Meteorological Department and National Disaster Warning Center. Data from the buoy is available at http://www.ndbc.noaa.gov/station_page.php?station=23401NOAA will deploy a second DART buoy farther south in spring 2007. The DART buoys are two of 22 tsunameters planned for the regional tsunami warning system in the Indian Ocean, which will provide warnings for Indonesia, India, Maldives, Sri Lanka, and Thailand. Other features of the final warning system will include tide gauges, modeling, and upgrades to communications.

The California tsunami of 15 June 2005 along the coast of North America

An Mw = 7.2 earthquake occurred on 15 June 2005 (utc) seaward of northern California off the west coast of North America. Based on the earthquake location and source parameters, the West Coast and Alaska Tsunami Warning Center issued a tsunami warning for the region extending from the California‐Mexico border to northern Vancouver Island, British Columbia (the first tsunami warning for this region since the 1994 Mw = 8.2 Shikotan earthquake). Six tide gauges on the west coast recorded tsunami waves from this event, with a maximum trough‐to‐crest wave height of 27.7 cm observed at Crescent City, California. Waves of 2.5 to 6.5 cm were measured at the five other sites: Port Orford (Oregon), North Spit and Arena Cove (California), and Tofino and Bamfield (British Columbia). The open‐ocean Deep‐ocean Assessment and Reporting of Tsunami (DART) buoys, 46404 and 46405, recorded tsunami waves of 0.5 and 1.5 cm, respectively, closely matching wave heights derived from numerical models. Incoming tsunami wave energy was mainly at periods of 10 to 40 min. The observed tsunami wave field is interpreted in terms of edge (trapped) and leaky (non‐trapped) waves and a “trapping coefficient” is introduced to estimate the relative contribution of these two wave types. Due to the high (3000 m) water depth in the source area, approximately two‐thirds of the total tsunami energy went to leaky wave modes and only one‐third to edge wave modes. The improved response to and preparedness for the 2005 California tsunami compared to the 1994 Shikotan tsunami is attributable, in part, to the operational capability provided by the open‐ocean bottom‐pressure recorder (DART) system, higher quality coastal tide gauges, and the effective use of numerical models to simulate real‐time tsunamis.

Natural Disasters: Building a Tsunami Warning System

The 26 December 2004 tsunami that devastated coastal areas in Indonesia, Malaysia, Thailand, Myanmar, India, the Maldives, Sri Lanka, and Somalia was produced by a magnitude 9.0 earthquake 155 kilometers southwest of northern Sumatra. The tsunami inundated coasts with waves more than 30 feet high every 30–40 minutes for several hours. It killed more than 150,000 people and injured millions, making it one of the worst natural disasters the modern world has ever seen. Could populations have been warned in advance? Not with the tsunami monitoring networks that exist in the affected area today, say officials with the National Oceanic and Atmospheric Administration (NOAA). Unlike the Pacific Ocean, which is wired for tsunami alerts by the United Nations Intergovernmental Oceanographic Commission, the Indian Ocean is largely devoid of comparable sensor technologies that detect earthquakes and issue tsunami warnings to affected countries. According to NOAA officials, future warnings could be enhanced by the creation of an Indian Ocean tsunami warning center that would deploy coastal tide gauges to measure the amplitude of waves near tsunami source areas such as fault zones and volcanoes, and would establish a communications infrastructure to send and receive alerts. Tsunami buoys also would be useful in an early warning system, NOAA officials say. At present, a network of six buoys is deployed by NOAA off the Aleutian Islands in the Pacific Ocean. This network, called Deep Assessment and Reporting of Tsunamis, is composed of two parts: a sea floor sensor and a buoy that relays tsunami information to warning centers on the ground by satellite communication. NOAA estimates that about 50 such buoys are needed to adequately cover the world’s oceans. On 6 January 2005 Senator Joe Lieberman (D–CT) proposed a $30 million package to develop these additional buoys, which the U.S. Congress is currently considering. Australian scientists are also designing an Indian Ocean tsunami alert system that is expected to cost US$20 million. Still more help could come from the sky. On 10 January 2005, NOAA announced that its scientists had measured the height of the December 26 tsunami using data from four Earth-orbiting satellites passing over the affected area at the time. NOAA geophysicist Walter H.F. Smith said in an agency press release that the best application of satellite data to improve tsunami hazard forecasts may be in helping to map the ocean floor from space. To be truly effective, any tsunami warning system will need to be part of an overall disaster reduction strategy, says Helen Wood, senior advisor for systems and services in NOAA’s National Environmental Satellite, Data, and Information Service. “You don’t want a separate system that segregates tsunamis from earthquakes or cyclones, because populations on the coast are at risk from any and all of those things,” she says. Wood heads the secretariat for the Global Earth Observation System of Systems, an emerging international coalition that has set disaster reduction as one of nine priority areas [see “Terra Cognita: Using Earth Observing Systems to Understand Our World,” p. A98 this issue]. “We had already identified tsunami and related instrumentation as a necessity,” Wood says. “Now there’s a sense of urgency. [The December 26 tsunami] was a catalyst for action. It’s sad, but disaster often mobilizes people at all levels to take action.”