arizona broadband seismic network is in the house
MIMI DIAZ, ARIZONA GEOLOGICAL SURVEY
In the last issue of Arizona Geology, we brought you the news of the nearly $500,000 FEMA Pre-Disaster Mitigation (PDM) grant awarded to the Arizona Geological Survey (AZGS) to acquire eight seismometers from Earthscope’s USArray project. The purpose of this project is to re-evaluate Arizona’s seismic hazard (which may actually be underestimated) and provide a comprehensive seismic update for hazard mitigation plans across the state. In this issue, we are bringing you news of the successes and challenges of starting up Arizona’s first nationally-integrated seismic network, one of the first steps in the seismic hazard analysis process.
To do a thorough job of analyzing seismic hazard for Arizona, several critical pieces are needed. We need historical seismic data; we need results from various local and regional seismic investigations to be integrated with the waveforms scribed by the seismometers; and we need current seismic data. We also need a seismic network that is funded to last beyond the duration of the PDM grant.
Prior to USArray, seismometers in Arizona were limited to six (analog) devices operated by the Arizona Earthquake Information Center (AEIC) at NAU, two reference network stations as part of the Advanced Network Seismic System (ANSS), and a smattering of temporary seismometers deployed for specific research projects whose data were not archived in any of the seismic catalogues. AEIC worked with the University of Utah Seismograph Stations (UUSS) to handle the data and provide near real-time information for the Northern Arizona Seismic Belt. To do a proper job of analyzing earthquakes with really low magnitudes (background seismicity), data from at least eight seismometers are needed. By contrast, UUSS has about 178 seismometers; California has about 2500.
With the advent of USArray (which has now completely departed Arizona) and the PDM grant, we now have four national reference network stations and eight broadband seismometers, which we chose strategically across the state. This brings the total broadband seismometers in Arizona to twelve, and analog at six. We call the eight new seismometers the Arizona Broadband Seismic Network (ABSN) and we are working to integrate the analog seismometers at AEIC and data from the ANSS seismometers into what we call the Arizona Integrated Seismic Network (AISN).
In the coming months, AZGS will be launching AISN in order to truly begin the process of melding the different seismic datasets together. We envision AISN as a one-stop shop for Arizona earthquake information. Our chief goal is to serve as an umbrella organization connecting seismic networks and equipment, creating a portal to seismic information generated by AISN’s cooperating partners (listed below), providing a source of seismic hazard information for emergency managers, and conducting public outreach.
Performing a state-wide seismic analysis is no mean task—we face several challenges to make it work. One of the challenges is to develop the capability to run a seismic network on our own. We have contracted with the Incorporated Research Institutes for Seismology (IRIS) to operate, maintain, and manage the ABSN data until we can do this ourselves. Another significant challenge is integrating the various networks (different datasets, different types of seismometers (velocity versus acceleration, analog versus broadband, etc.) and seismology projects so that we have the maximum amount of quality data with which to perform the new seismic hazard analysis. Fortunately, we have top-notch geoscientists participating in the project across the state.
One of our biggest challenges, however, is securing the funding to operate and maintain the ABSN and the AISN beyond the life of the grant. AZGS has established an account to handle tax-deductible donations for those who wish to “adopt” a station (seismometer). We can accept donations of any size.
If you have access to deployed seismic equipment (with high quality data that meet the IRIS Data Management Center standards) and would like to become a part of the Arizona Integrated Seismic Network, or if you are currently involved in seismic research that AZGS is not aware of, please contact Mimi Diaz, at email@example.com or (602) 708-8253.
The new Arizona Broadband Seismic Network (ABSN) was made possible by a joint coalition of AZGS (Mimi Diaz, Dr. Phil Pearthree), Arizona State University (Dr. Matt Fouch, Dr. Ramon Arrowsmith), Northern Arizona University (Dr.David Brumbaugh), and the University of Arizona (Dr. Susan Beck, Dr. George Zandt), who provided matching funds and are carrying out the project. Emergency management offices from fourteen of Arizona’s fifteen counties and the Arizona Division of Emergency Management support this project.
We thank the following for graciously permitting AZGS to continue operating seismometers on their property: Wellton-Mohawk Irrigation District (Yuma County); Glenn Ranch Corporation (Cochise County); Kaibab National Forest (Navajo County); Mohave County Parks; Grand and Michelle Reidhead (Navajo County); and Jack and Carey Sigler (Maricopa County).