April 24, 2012

Satellites and Security Series: Enhancing Tsunami Detection and Response

One of the research areas that we at CNAS have been exploring for the last several years is how the United States can make better use of satellites to enhance its understanding of the environment and the potential security consequences of environmental and climate change. In August 2010, for example, Christine Parthemore and I published a study exploring the decline of America’s Earth monitoring satellite capability and its implications for U.S. national security (See Blinded).

Our research has taken us to new areas of exploration, including how the United States can make better use of satellites to respond to natural disasters and provide humanitarian assistance and disaster relief (HA/DR). Given that climate change could portend a future that may demand increased support from the United States to conduct HA/DR missions, it behooves national security policymakers to identify what tools and techniques the United States should have to adequately respond to future disasters.

Although not linked to climate change, tsunamis are an area that has drawn our attention as of late, especially in the wake of the March 2011 disaster in Japan. With demographic trends in Asia suggesting that more people are moving to coastal communities in seismically active regions (i.e, the Pacific Ring of Fire), more people could be vulnerable to earthquake-induced tsunamis. How should the United States think about ways to enhance its tsunami early warning system that can provide forewarning to coastal residents? NOAA’s Deep-ocean Assessment and Reporting of Tsunamis (DART) program that relies on a set of floating buoys to provide accurate readouts of tsunamis is facing budget cuts.  As a result, the United States may actually be trimming back a critical capability that could be of greater demand in the future.

Could satellites offer an opportunity to enhance tsunami early warning systems that are cost effective and provide efficient notice to vulnerable communities? Potentially.  Some of the existing (and interesting) proposals are still largely in research and development, so it is unclear of their costs when brought to scale, but they could potentially make good use of satellite systems to provide better information about an earthquake’s magnitude and the potential size of any tsunami generated by the seismic event – information that is critical to improving evacuation notices and determining the extent of the evacuation zone.

In a recent report by Nature, scientists are exploring ways to use Global Positioning System (GPS) satellites to improve seismic measurements that would help scientists better understand the size of tsunamis. An integrated ground-satellite system measures the displacement of a ground sensor by an earthquake. Put simply, the satellite knows where the GPS ground sensor is supposed to be. After an earthquake, scientists use GPS satellites to measure the movement of where a ground sensor is versus where it was supposed to be. This measured change can be put into a model that helps scientists quickly determine the true magnitude of the earthquake.

In contrast, “seismometers have limitations,” according to the Nature report. "‘They do a beautiful job discriminating among magnitude 2, 3, 4, 6, earthquakes,’ says [Tim Melbourne, a geodesist at Central Washington University in Ellensburg]. ‘But they run into trouble where you have to distinguish a magnitude 8 from a magnitude 9.’ This is partly because in big quakes, the ground may shake for longer, but not significantly harder.”

“GPS has no such problem, because it directly measures the movement of the ground,” the report states. "‘If the ground lurches by many metres, it's unambiguous evidence for a very large earthquake,’ says Susan Hough, a seismologist at the US Geological Survey in Pasadena, California.”  What is more, the report notes, the measurements help scientists determine the size of the quake (and potential tsunami) about ten times faster compared to using seismometers.

This is just one of many interesting ways scientists are thinking about using satellites to improve disaster detection and response. Again, it is unclear how the costs compare to existing systems, but the proposals have some promising potential, especially if they can enhance existing capabilities (especially since current capabilities may be in decline). We’ll continue to highlight these technologies and approaches as we discover them in our research. If for no other reason we hope it’ll help security practitioners think more creatively about what tools they can use/need to do their jobs. They may be surprised.