How NCEI’s data makes a real-world difference before, during and after tsunamis
Tsunamis can be devastating, unpredictable events that have caused over 250,000 fatalities since the beginning of the 21st century—as well as hundreds of billions of dollars in damage to property and infrastructure. The harrowing scale of the destruction they cause can raise doubts over the difference that mere data can make. While no amount of tsunami data can prevent the disasters from occurring, collecting and storing it saves countless lives.
The Database
NCEI stewards one of the only global historical tsunami databases, which contains information such as the date, time and location of tsunamis, their magnitude and intensity and the maximum height of the resulting tsunami wave. The database also includes information about their impact—such as the total number of casualties and monetary damage—and images of the tsunamis’ aftermaths.
The database is a crucial source for understanding tsunami generation, propagation and wave behavior. Also included in the archives are Digital Elevation Models (DEMs), which incorporate bathymetric and topographic data to produce visual simulations of hypothetical tsunamis and the effect they would have on the modelled region. DEMs can be used to predict tsunami arrival times, wave propagation and runup heights as well as inundation along the coast, all of which is crucial for warning efforts.
Tsunami Warning Centers
Tsunami data proves indispensable for the National Weather Service’s (NWS) Tsunami Warning Centers in Hawaii and Alaska. Their main responsibility is to issue warnings to the public of impending tsunamis so that evacuations can take place. A tsunami is typically caused by an offshore earthquake, whose seismic waves travel 100 times faster than the tsunami itself. Because of this, the centers get a head start by analyzing data collected from seismic networks, such as the earthquakes’ location, depth and magnitude. If this information points to a possible tsunami, the centers then examine changes in water levels detected by coastal measuring stations and the Deep-ocean Assessment and Reporting of Tsunamis (DART) buoy system. The latter is a real-time tsunami monitoring system developed by the NOAA Center for Tsunami Research (NCTR) at the Pacific Marine Environmental Laboratory, which also develops crucial tsunami flooding models. Based on these findings, as well as the tsunami simulations provided by the DEMs, the NWS centers will issue alert levels for the U.S. coastlines, which may change for certain locations as new information becomes available. The alert levels are as follows:
1. Information statements: No threat or very distant event for which hazard has not been determined
2. Watches: Potential hazard not yet known
3. Advisories: Strong currents and waves dangerous to those in or very near water
4. Warnings: Dangerous coastal flooding and powerful currents expected
NCEI makes tsunami wave data available once the event is over, and Tsunami Warning Centers rely on the historical tsunami data to establish thresholds for the tsunami alert levels described above. The post-event data may come from coastal tide gauges or ocean bottom pressure recorders, but a significant amount of data comes from field reconnaissance surveys, where tsunami wave height or runup data is collected along a coastline. The post-tsunami survey data adds information in locations where permanent data recorders—such as tide gauges—are not present. Post-tsunami surveys collect data in a wide variety of locations and environments to paint a more complete picture of the variation in runup and inundation along the coastline in a tsunami event.
Hazard Assessment
In the 21st century, an average of 14 tsunamis have been observed per year globally, with typically only one or two tsunamis in a year being damaging or deadly. However, unlike meteorological disasters, the time and location of a tsunami’s occurrence is nearly impossible to predict, leaving vulnerable regions with little time to brace themselves. Hazard assessment carried out by organizations like the NCTR focuses in part on analyzing historical data to identify hazard zones where tsunamis are known or expected to occur. NCEI’s data guides many efforts in these areas, such as improving evacuation routes, designing and building tsunami-resistant structures and, in particularly vulnerable areas, guiding future development.
Educating the Public
While much emphasis is placed upon fortifying vulnerable regions against the financial impact of tsunamis, the protection of human lives takes precedence over all else. The hazard assessment made possible by NCEI’s database also allows for education efforts tailored specifically to a vulnerable population’s needs, which may vary depending on factors such as the historical severity of the tsunamis that affect it. The NWS TsunamiReady program in particular offers recognition to vulnerable regions if they meet its guidelines, which includes the implementation of tsunami education to the public in the form of signage, outreach materials, community exercises, school programs and more. Additionally, the National Tsunami Hazard Mitigation Program provides a framework to support the collaboration and coordination between federal, state and territory partners to reduce the impact of tsunamis.
