Using the Caltech Community Seismic Network for Early Warning

Session: Earthquake Early Warning: Current Status and Latest Innovations [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

ShakeAlert currently uses continuous, low-latency, 100 sps, 2-g clip, seismic data streams that are provided by regional networks operated along the U.S. West Coast. 1,300 stations are planned for the full implementation by 2025. The average station spacing will be about 25 km (less in urban areas) and the average time required for a P-wave to trigger four stations will be about 5 s. Increasing the number of stations by a factor of 10 would decrease that to about 1 ½ s. Given the difficulty of achieving the current station buildout plan, it seems that a different type of seismic network is needed to achieve the station density needed for significantly shorter warning times.

The Community Seismic Network (CSN) operates about 450 stations in urban Los Angeles (expanding to 550 in 2020). CSN stations consist of low-cost Linux plug computers and 3-component, 16-bit, 2-g clip, mems accelerometers. Most stations are located at campuses of the Los Angeles Unified School District with a station spacing of less than 2 km. Data telemetry is via the Internet. Short messages (updating the times and amplitudes of pga > 0.1% g) are transmitted to Caltech within 20 ms of real-time. This pga data is then merged with pga data from CISN stations in a development version of Finder. Finder uses the spatial pattern of pga to map the spatio-temporal evolution of rupture. The high station density of CSN means that Finder is as fast as point source algorithms (e.g., EPIC) for earthquakes located within the CSN network. CSN pga picks can also be utilized by the PLUM algorithm, which is used by JMA to characterize evolving wavefields in real time. Since CSN real-time data feeds are parametric, there is no need to achieve high telemetry rates during significant events. This eliminates the requirement of the existing ShakeAlert system to secure high-rate telemetry links to ensure that continuous, low-latency, data is available to the central processing units.

Presenting Author: Thomas Heaton

Authors