Arizona’s Broadband Seismic Network (ABSN) finally has statewide coverage
The Arizona Geological Survey’s broadband seismic network (ABSN) has reached a significant milestone. For the first time ever, multiple seismic stations are in place and provide a statewide seismic monitoring network that can be used to estimate seismicity rates, the amount of ground-shaking and can provide seismic data that can be used to image subsurface processes. Many people in Arizona do not know that Arizona experiences earthquakes and that although infrequent, damaging earthquakes do occur (Map of earthquakes and active faults).
Within the past year the AZGS has more than doubled the size of the statewide seismic network with the addition of 6 broadband stations installed by the end of 2017, and the recent adoption of two stations from the Earthscope Transportable Array project. The AZGS now operates and maintains 15 broadband seismic stations, and together with two other stations operated by the United States Geological Survey, there are a total of 17 broadband seismic stations throughout the state. These stations continually provide waveform data for local, regional and global quakes, and nuclear explosions. The data are continually archived at a international data management center operated by the Incorporated Research Institutions for Seismology (IRIS).
The AZGS is updating the computing systems that take in the real-time seismic signals so that they can be used to detect earthquakes in the lower magnitude range (less than M3.0). The current system can detect quakes down to M3.0 for a good portion of the state, but AZGS’ goal is to detect all earthquakes within the state down to M3.0. For areas with higher populations, and seismic activity, the goal is a detection threshold of M2.5.
Figure 1. Map of Arizona with location of earthquakes (shown as circles) and active faults (shown as lines of green, orange and purple). AZGS seismic station location shown as red triangles. USGS/GSN stations shown as blue triangles. The majority of recorded earthquakes have occurred mostly in the northern half of the state. Large quakes originating in California, Mexico, as well as Utah and Nevada have caused significant ground-shaking within Arizona.
Figure 2. Installation of a post-hole style broadband seismometer (tall steel cylinder on the right). The seismometer is tested in the lab with a special digitizing computer system prior to installation. Once the location is found and permitted, the seismometer is placed several meters down within sealed casing. The rest of the installation includes equipment that can digitize the seismic signals, generate sustained power, and a communications system that can send the data to the AZGS data acquisition system in real-time.
Posted by Jeri Young Ben-Horin (AZGS Research Scientist)