A Fault Hazard Based Expected Value Metric for Earthquake Early Warning Seismic Network Stations

Date: 4/24/2019

Time: 06:00 PM

Room: Fifth Avenue

Funding agencies and network operators are interested in ways to measure the performance benefits from investments in new and existing seismic stations. Biasi and Alvarez (SSA Annual, 2018) showed that the contributions of individual stations and telemetry investments to EEW could be expressed in physically meaningful units using alert time improvement and area of coverage improvement. This work used the alert time calculator of Hotovec-Ellis et al. (SRL, 2017). A grid of hypothetical earthquake source points is assumed, and EEW alert times to some central point are then calculated. A candidate new station is added to the original station coverage, and alert times recalculated. The new station decreases time to alert in some area around it. The integral of time improvement over this area has units of km^2-seconds. The impact of station removal (say, due to a maintenance problem) is computed the same way except for the sign of the effect.

The time-area metric can say nothing about whether the station would actually contribute to EEW without some estimate of earthquake activity nearby. The seismic engineering metric of return time is here adapted to add the expected utilization component. The corresponding return time reflects how often the station is expected to contribute to EEW based on the fault hazard.

The approach is readily implemented in California using the fault model and earthquake rupture rates in the Uniform California Earthquake Rupture Forecast v.3 (Field et al., 2014). The return time at a ground level of EEW significance (e.g., peak ground acceleration (PGA) = 5 cm/s/s) is combined with the alert time-area metric to become an expected value in km^2-s/yr. Consistent with intuition, the expected value metric favors stations filling modest holes in a network near high slip rate faults and large holes beside low slip rate faults.

Presenting Author: Glenn Biasi

Authors