Seismic Background Noise PSD in Northern and Central California

The density and distribution of broadband seismic stations located in Northern and Central California increased during the past few years, with two new BK stations and additional broadband seismic stations installed as the USArray transportable array completes its station coverage in the region. One design goal of the transportable network has been to complement the existing BDSN broadband stations and cover the region with an average interstation spacing of $\sim$70 km. We have been using data from the USArray TA stations and monitoring station quality through the analysis of the seismic background noise PSD level observed at the transportable stations. This is, in part, so that we can choose the best sites to continue occupying after the transportable array moves out of the region, in order to improve the coverage of the BDSN network. Based on this analysis as well as criteria such as ownership and access to power and telemetry, seven stations have been selected for upgrade to permanent sites within the next 18 months. These are: V04C (RAMR), HAST, P01C and S04C, as well as HATC, HELL and SUTB (see Figure 3.2.