Geoscience Reference
In-Depth Information
Box 2.4
Near Real-Time Analysis of Earthquakes and Volcanic Eruptions
With rapid growth of human population, society faces increasing exposure to
catastrophic effects of earthquake faulting, tsunamis, and volcanic eruptions. As basic
scientific investigations of these phenomena advance, a natural result is that observational
and analytic procedures mature to the point where they can be robustly and rapidly applied,
even while the event is under way. This exercise of scientific understanding can enable
development of real-time hazard warning systems to society's great benefit, both from early
warning of imminent shaking or tsunami arrivals and by providing guidance to effective post-
event emergency response activities. While continuous environmental monitoring is typically
the function of mission-driven agencies, development of the fundamental understanding on
which real-time warning capabilities can be based involves NSF-funded research on natural
phenomena.
Early warning systems rely on continuous acquisition of data from potential source
regions, and real-time telemetry of the data or local analysis products for events as they
occur to central processing centers where the signals enable near real-time evaluation of the
process and its hazards, launching appropriate communications about the event and its
potential distributed impact. For earthquakes and volcanic eruptions, such methodologies can
exploit the finite velocity with which seismic, tsunami, or air-blast waves spread from the
source relative to electronic communications to warn nearby regions before the waves arrive.
Automated systems that sense initial signals can also activate immediate responses locally to
mitigate the impact of later-arriving signals. These strategies are exemplified by ocean-scale
tsunami warning systems, such as the National Oceanic and Atmospheric Administration's
(NOAA) Pacific and Alaska Tsunami Warning Systems, and the Shinkansen (Japanese bullet
train) accelerometer system for stopping trains when P wave ground motions exceed certain
thresholds (in advance of later-arriving, stronger S wave and surface wave ground motions).
The potential for many applications to mitigate shaking damage given from seconds to hours
of lead time after occurrence of an event is just beginning to be explored.
Rapid analysis and warning of large earthquake ruptures can potentially be achieved
with integrative approaches using geodetic (continuous, high-sample-rate GPS), seismic
(rapid local network event location, mechanism, and finite faulting determination), and ocean
measurements (water pressure and geodetic systems that detect tsunami waves offshore).
Such applications are rapidly emerging, and over the next decade significant enhancements
and impacts from these capabilities can be exploited. The Cascadia subduction zone is being
instrumented onshore and offshore using EarthScope and American Recovery and
Reconstruction Act funding. These regional seismic and geodetic networks within one venue
of natural hazard exposure are valuable for advancing the basic science underlying rapid
warning capabilities. Significant progress has been made in developing remote tsunami
warning capabilities, but close-in tsunami warning, where warning response times of only
tens of minutes are required, presents great challenges. This drives basic science efforts to
establish what aspects of large offshore earthquakes can be reliably characterized in ground
motion signals soon after an event initiates and the extent to which the ultimate size of the
event can be anticipated early in its process. Similar challenges exist for developing rapid
warning of volcanic eruptions that present hazards to air traffic. Development of seismic,
geodetic, and infrasound analysis that can establish the occurrence of strong tropospheric
and stratospheric blasts and ash clouds requires better understanding of explosive eruption
processes and their manifestations.
Data from EAR facilities in seismology (IRIS), geodesy (UNAVCO), EarthScope, and
community organizations (SCEC, GeoPRISMS) provide the means for coordinated efforts to
rapidly analyze signals from active processes. Ultimately, monitoring and implementation of
warning systems are the provenance of the USGS and/or NOAA (for Homeland Security), but
developing and integrating the scientific approaches remain a basic science problem, as
extensive fundamental understanding of the processes and the signals they generate lies at
the core of all early warning strategies. Rapid analysis and quantification of earthquake and
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