This interferogram of the magnitude 7.2 Baja California earthquake of April 4, 2010, overlaid atop a Google Earth image of California's Coachella Valley - Salton Sea region, was produced by the UAVSAR synthetic aperture radar aboard NASA's Gulfstream III research aircraft. NASA Dryden is evaluating earthquake warning seismometers developed by Seismic Warning Systems, Inc., to determine if sonic booms could cause false alarms. (NASA/JPL/USGS/Google)
NASA's Dryden Flight Research Center and Seismic Warning Systems, Inc., are evaluating the company's QuakeGuard™ earthquake warning system to determine if sonic booms cause the devices to register false alarms.
Under a NASA Space Act agreement, the company has installed two of their QuakeGuard™ warning seismometers at NASA Dryden. The system is in test mode, not warning mode. The devices were installed in Dryden's main office building, spaced about 100 feet apart and tied into the building's foundation. Vertical accelerometers in the devices, using the company's proprietary algorithms, are designed to detect precursor or "P" waves that travel ahead of the primary, destructive "S" shockwaves of earthquakes.
So far, normal sonic booms are not causing the system to generate false alarms. But Dryden, in an effort dubbed SonicBREWS, or Sonic Boom Resistant Earthquake Warning System, is going to put the system to the test during three flights that will have F/A-18 aircraft dive to place sonic boom shockwaves directly on the building, thereby better mimicking the P waves.
Such a system is currently installed in California's Coachella Valley, with warning devices installed in several schools and fire stations. The system worked during one of California's most recently felt quakes, the 7.2-magnitude Baja California earthquake that occurred on April 4, 2010, the strongest in the region in 18 years. The earthquake was larger than the devastating 7.0 Haiti earthquake last January.
The QuakeGuard™ system successfully detected the Baja quake's P wave 90 seconds before the arrival of the quake's S waves and set off alarms that included the automatic raising of local fire station doors that are integrated into the system. During earthquakes, fire station doors are frequently jammed shut, interfering with local fire department response to the events.
Depending on the geographic distance from an earthquake epicenter, officials estimate such warning systems could provide up to five minutes warning prior to the arrival of a distant quake, but only seconds for a device located near the epicenter. Though 90 seconds may sound like little warning, even less time is enough time for people to duck-and-cover, for automated valves on gas company pipes to shut off gas, and for fire station doors to open, etc.
Plans are in formulation for installation of such a system in the Lancaster – Palmdale area in Southern California, which lies adjacent to the San Andreas Fault about 70 miles northeast of Los Angeles. Due to the frequency of sonic booms in that area from flight test aircraft operating out of nearby Edwards Air Force Base, Seismic Warning Systems needs to see whether sonic booms need to be filtered out of the system.
Additionally, Dryden is working with Seismic Warning Systems on a white paper study of the technology and the effects of sonic booms, or the lack thereof, on it's capabilities.
Gray Creech, public affairs
NASA Dryden Flight Research Center