Earthquake early warning systems
More accurate sensors that track the speed difference between P-waves and S-waves created by fault ruptures have facilitated the development of effective earthquake early warning systems. Japan has been using this technology since the 1960s to stop bullet trains and prevent earthquake-induced derailments. The seismically active Palm Springs, California, area adopted this technology in the 1980s to increase the speed of fire department response. The U.S. Geological Survey, California Institute of Technology at Pasadena, University of California at Berkeley, California Office of Emergency Services, and other agencies and organizations are partnering to create a public warning network for the heavily populated earthquake-prone areas of Los Angeles and San Francisco.
Earthquake early warning (EEW) enhances resilience by encouraging investment in retrofitting for seismic strengthening, by developing policies for responding to the warnings, and through public education about the meaning of warnings and appropriate responses to them. Challenges remain, however, in the development of effective public warning within the blind zone near the epicenter of an earthquake where the time difference between the P- and S-waves is so short that no warning can be issued, as was demonstrated in the 2014 Napa Earthquake. Other challenges include the high cost of developing and maintaining public EEW systems. This chapter discusses how these challenges factor into the design of such a system.