To meet EarthScope's scientific goals, hundreds of stations have been installed across the country, including a 3.2km borehole into the San Andreas Fault.
A backbone network of 116 new and 20 existing GPS receivers provide a long-wavelength, long-period synoptic view of the entire plate boundary zone including the eastern US. Additionally, a focused dense clusters of 775 permanent GPS receivers are dedicated for observation along fault zones and magmatic centers in western North America and Alaska. Strainmeter strain rate sensitivity reaches a maximum at a period of a week and then decreases at longer periods due to an increase in the amplitude of the short baseline Earth noise spectrum. In real time, at long periods (months to a decade) GPS has greater sensitivity than strainmeters by one to two orders of magnitude. At intermediate periods (weeks to months) sensitivities are comparable, and at shorter periods (seconds to months) strain sensitivity is one to three orders of magnitude greater than GPS.
A transportable array of 400 portable, unmanned three-component broadband seismometers deployed on a uniform grid that is systematically covering the US. Each USArray station includes the instrumentation necessary to continuously sense, record, and transmit ground motions from a wide range of seismic sources, including local and distant earthquakes, volcanic eruptions, and other natural and human-induced activities.
USArray has a large traveling network of 400 high-quality, portable seismographs that are being placed in temporary sites across the United States in a rolling fashion. Station spacing is ~70 km (42 mi) called the Transportable Array. Transportable Array data are extremely useful for mapping the structure of Earth's uppermost 70 km. The array was initially deployed in the westernmost United States. Unless adopted and made into a permanent installation, after 18-24 months, each instrument is picked up and moved to the next carefully spaced array location to the east. When completed, over 2000 locations will have been occupied during this program. More information about adopting a station can be found at the USArray webpage on adopted stations.
Atmospheric Sensors on Transportable Array
TA stations are now being equipped with Atmospheric Sensors as of 2010. In addition to the Micro-Electro-Mechanical (MEMS) state-of-health barometer included within the vault at all installations since 2004, each station also features an external high frequency infrasound microphone (NCPA model IFS-4532) and a low to intermediate frequency microbarometer (Setra 278). The compared responses of all three instruments demonstrate the wide spectrum of atmospheric signals now recorded. For more information about the Atmospheric Sensors, visit the USArray webpage.
The magnetotelluric (MT) component of EarthScope’s USArray consists of both permanent and portable elements that measure naturally occurring electric and magnetic fields. The backbone component consists of seven permanent MT stations installed across the United States as a reference network. These data are integrated with other geophysical data to identify Earth's thermal structure and study the significance of fluids in the crust.
Twenty-one transportable MT systems complement the seven permanent MT stations. The transportable MT instruments are being used for deployments of approximately one-month duration on a nominal 70-km grid spacing for imaging of crustal and lithospheric conductivity structure in areas of special interest as proposed by the MT community and approved by NSF.The MT stations and instruments are operated and maintained by Oregon State University under a subaward from IRIS. For more information about the Magnetotelluric Array, visit the USArray webpage.
The long-base laser strainmeter (LSM) is an example of an extensometer, which measures the change in length along a line. Borehole strainmeters measure strain change by very accurately sensing change in the shape of an instrument cemented into rock. Because the dimensions of the instrument are only a few inches, very precise measurements are required. A typical signal is 10 nanostrain = 0.000 000 001mm across the instrument.
Campaign / Flexible
Campaign/Flexible instruments allow for focused observation and study of key geophysical locals and are available to the scientific community through proposals approved by the NSF. These instruments can be used to augment the permanent instruments, extend investigations into Canada and Mexico, and respond to volcanic and/or tectonic crises. More info on Campaign/Flexible here.
Synthetic Aperture Radar (SAR) imagery was acquired as part of the GeoEarthScope project. Guided by the GeoEarthScope InSAR Working Group, more than 17 terabytes of data suitable for interferometric analyses were purchased from the European Space Agency (ESA) and ordered from NASA via the Alaska Satellite Facility (ASF). Included were data from ESA's ENVISAT, ERS-1 and ERS-2 missions as well as the Canadian Space Agency's RADARSAT-1 mission. In addition to ordering data from existing ESA and NASA archives, UNAVCO tasked the ESA ENVISAT satellite to acquire new SAR data for EarthScope regions of interest for every orbit from October 2007 through September 2008. The UNAVCO Facility Data Group developed and implemented the essential infrastructure and software needed to archive the GeoES data and to support community access to this rich dataset. EarthScope InSAR data products are available from the UNAVCO SAR Archive.
5,788 km2 of high-resolution airborne LiDAR imagery was acquired as part of GeoEarthScope, a component of the EarthScope Facility construction project funded by the National Science Foundation. Targets were identified by the GeoEarthScope LiDAR Working Group and consisted in most cases of 1~2 km wide corridors centered along active faults. LiDAR acquisitions were planned and conducted based on EarthScope community recommendations so as to provide the community with a rich, high-quality data set capable of supporting a wide range of interests and applications. EarthScope LiDAR data products in various formats are available from the Open Topography Portal. Currently available GeoEarthScope datasets include acquisitions from Northern California , Southern California , and the Intermountain Seismic Belt .