EarthScope is an integrated research effort designed as a distributed, multi-purpose geophysical instrument array that has the potential for making major advances in our knowledge and understanding of the structure and dynamics of the North American continent. This knowledge is not only important scientifically but is important socially because of its use in mitigating the impact of the infrequent, but increasingly costly, disasters caused by earthquakes and volcanic eruptions.
Advances in theory, computing and the technology of optical and radio telescopes have allowed us to see ever deeper into the universe overhead. Similarly, theoretical, computational, and technological advances in seismology, extraterrestrial geodesy, and drilling provide the tools to make major advances in looking downward into the planet. High-precision geodesy using the Global Positioning System (GPS) is mapping the large-scale deformation field in space and time. Interferometric Synthetic Aperture Radar (InSAR) represents a complementary means of mapping deformation over broad areas with high spatial resolution. A new generation of seismometers can now provide detailed images of crust and mantle structure, as well as our best look ever at the earthquake process. Strainmeters give us nano-strain sensitivity with the ability to measure short-term aseismic deformation transients that provide insight into the processes of earthquake nucleation. Advances in drilling technology made by the petroleum industry have brought new science objectives, previously unattainable because of intractable drilling problems, within our reach. Significant technological advances are taking place in microelectronics, data collection systems and communication, allowing the miniaturization of downhole instrumentation and the efficient real-time handling of vast volumes of data from large arrays of geophysical instrumentation.
Initial results from these new technologies, coupled with multidisciplinary integrative approaches to scientific discovery and management, demonstrate the potential for significant advances. For example:
SCEC, with two years remaining under the NSF/STC program, has started planning for its future. SCEC intends to expand its focus on the physics of earthquakes (i.e., those processes leading up to and including earthquake nucleation, fault rupture, and the ensuing ground motions) with a practical aim of improving earthquake forecasting and seismic hazard assessment. It will employ a multi-disciplinary, integrative (systems) approach to problem solving Ð similar to that pioneered by SCEC with its "master model" approach to earthquake science and hazard analysis. Numerical modeling and simulations of fault evolution, rupture propagation and ground motions will play an enhanced role in the future. Products will include complete theoretical seismograms for plausible future earthquakes that can be used by engineers for performance-based engineering design.
The implementation strategy of EarthScope is staged as follows:
Stage I. A) USArray, and B) San Andreas Fault Observatory at Depth
Stage II. Plate Boundary Observatory
Stage III. Interoferometric Synthetic Aperture Radar (InSAR)
Stage I of EarthScope is composed of two elements. The first element is the USArray, which is a dense array of high-capability seismometers that will be deployed in a step-wise fashion throughout the U.S. to greatly improve our resolution of the subsurface rheology. Figure 1 shows a schematic of the important earthquake processes in space and time along with the observational strategies. Below the cm level, laboratory investigations are effective. Above one-km scale, the observational fields of seismology, fault mapping, and crustal deformation are effective. The USArray will greatly improve the uniform resolution of crust and upper mantle rheology from the current 500-km resolution to about 30-km resolution, and special studies will show even finer detail to the 1-km level.
The second element of Stage I, the San Andreas Observatory at Depth, addresses the remaining uncovered observational gap in Figure 1, between 1 cm and 1km. This zone represents the range of nucleation and rupture processes of earthquakes. The physics of these processes is one of the most challenging problems in science today. A number of theories and inferences from laboratory and large scale (>km) observations have been proposed to model the dynamics of these critical events. Yet, there has been no observational means of testing these theories because of the difficulty of access, at reasonable cost, to an active fault at seismogenic depths. We are now in a position to do this and the San Andreas Fault Observatory at Depth is the means.
The acquisition, deployment and installation costs of EarthScope — Stage I are requested to be supported through the MRE account starting in FY 2001 and continuing through FY 2004 with a total request of $74.8 million. Support from the GEO Directorate/Earth Sciences Division for operations, science and management is estimated to total approximately $62 million over the 10 year period until FY 2010. Funding is planned to start at $2.5 million in FY 2001 and reach approximately $8 million per year by FY 2005. For Stage I, it is estimated that more than 160 U.S. scientists and a similar number of students will be involved in the operations and data utilization. We estimate foreign participation of more than 75 scientists and students.
Stage II involves the construction of a Plate Boundary Observatory (PBO) encompassing the western half of the US. The PBO is composed of an array of permanent borehole installations of multiple instruments, including GPS receivers, strainmeters, tiltmeters, and seismometers. The entire region west of the Rocky Mountains is dominated tectonically by the forces related to the movement between the North American and Pacific plates. The concept of the Plate Boundary Observatory was inspired by recent exciting discoveries showing the interconnectedness of fault systems and the non-seismic distortion of the crust and upper mantle that appear to be related to future seismic events.
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Figure 1. A schematic representation of the Earth's crust and mantle dynamics as a function of space and time. Earthquake nucleation and rupture processes occupy a spatial zone between about 1-cm to 1-km that is not observable without access to active faulting at seismogenic depths. (figure from J.B. Minster, personal communication, 1999) |
Stage III involves flying a synthetic aperture radar (SAR) on a satellite. Interferometric SAR (InSAR) has produced spectacular images of crustal distortion of earthquakes, volcanoes, and land subsidence with high precision and spatial resolution. This instrument will address much of the observational gap shown in the space/time plot of Figure 1. Because of the need for a satellite, NASA currently has the main role for InSAR. However, after more than eight years from proof of concept, budget restrictions have delayed NASA commitment even though the need is generally accepted. The current NASA plan, an Announcement of Opportunity named LightSAR, is now open for proposals with a decision on the successful proposal due in July 1999. An NSF partnership with NASA may be desirable to provide support to the data retrieval component of the project and protect the scientific uses of this critical technology.
Operational aspects of EarthScope will be coordinated through a federation of the participating consortia under cooperative agreements with NSF. Oversight for implementation, operation, and data acquisition and archival will be provided by a working group composed of the leaders of the participating consortia, plus representatives from involved government agencies. The consortia - SCEC, IRIS, and UNAVCO - have successfully managed comparable facility construction and operation, and work well together to maximize the value gained from agency funding, and set priorities on the basis of scientific merit and effective implementation of facility goals. The major agencies - NSF, USGS, NASA, and DOE - that will be involved have demonstrated the ability to collaborate effectively with each other and with the scientific community in efforts such as NEHRP (National Earthquake Hazard Reduction Program), SCIGN (Southern California Integrated GPS Network), and the Interagency Coordinating Committee for Continental Drilling. Research based on EarthScope data will be supported through the normal peer-review funding process at NSF, other US agencies, and other international agencies such as the International Continental Drilling Project (ICDP), and the overall effort will be tightly coordinated by a science steering committee. Utilization of the data for practical considerations will be closely coordinated with mission agencies at state and federal levels.
A unique feature of the EarthScope is the involvement of students and the general local community in the plans, installation, operation and analysis of results within each region of occupation. Significant benefit will be gained from the already ongoing support structure and concepts of the IRIS Education and Outreach program including the PEPP (Princeton Earth Physics Project), which features a seismic station at 55 participating high schools throughout the country. The high schools connect their seismometer to the Internet and have access to all other PEPP seismograph data for doing educational projects related to earthquakes and the structure of the Earth. EarthScope is envisioned to be the prominent catalyst for an exciting public education program.
Two components will comprise the education and outreach part of EarthScope. The first will be online real-time access to recorded data. The second is an organized, integrated, earth science program designed to go into an area before the USArray arrives and prepare people for the arrival of the array. This will include primers on earth structure, earth dynamics, earthquake hazard and interesting regional geologic features to be investigated by the array and ancillary geologic studies. There will be educational materials addressed to and made available to both the general public and local/state governments as well as for K-12 (as appropriate). While the array is in a region, the program will bring results from the array to the community. Finally, a follow-up program will continue to link communities to the array as it moves across the country and show how the data recorded by the array in their region merges with data from other regions that build a continuous image of lithospheric and mantle structure. One idea still in the conceptual stage is to provide a feed into the weather channel so that "significant event" data can be broadcast.
2001: Compete and award contracts for broadband and short-period seismic systems. Community planning on permanent seismic sites and first array deployment. San Andreas Fault Observatory at Depth main hole drilling contract competed and awarded. Drilling begins at end of year. Down-hole monitoring equipment constructed. NSF conducts review of plans and costs.
2002: Delivery and installation of 50 transportable array sites. Delivery and installation of 500 flexible pool short period sites. Delivery and installation of 5 GSN and 10 NSN permanent stations. Main hole completed at San Andreas Fault Observatory. Down-hole monitoring instrumentation installed. NSF conducts review of plans and costs.
2003: Delivery and installation of 200 transportable array sites. Delivery and installation of flexible pool sites: 200 broadband and 1000 short period seismic systems. Delivery and installation of 5 GSN and 10 NSN permanent stations. San Andreas Fault site characterization studies carried out.
2004: Delivery of 50 and installation of 200 transportable array sites. Delivery of flexible pool sites: 150 broadband and 500 short period. Installation of flexible pool sites: 200 broadband and 1000 short period. Delivery and installation of 5 NSN permanent stations. Use site characterization and monitoring data to chose four coring intervals at depth in San Andreas Fault Observatory. Commence coring operations. NSF conducts review of plans and costs.
2005: Redeployment of USArray continues at approximate 1.5 year intervals. Install permanent monitoring instrumentation in four core intervals and main hole of San Andreas Fault Observatory at Depth.
2006: Complete analysis of San Andreas Fault cores, cuttings and logs. Continue monitoring at depth. NSF conducts review of plans and costs.
2007:
2008: NSF conducts review of plans and costs.
2009:
2010: NSF conducts review of plans and costs.
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