This is a reworked version of the draft of Section 1 distributed at the January 2000 ExCom meeting. It uses the new forward written by Tom Jordan and makes a number of other changes. Prepared 2/9/00 by Peter Shearer.

The IRIS Proposal

"IRIS: The Next Five Years"

July 1, 2001 - June 30, 2006

submitted to the

National Science Foundation

by the

96 Member Research Institutions

of the

IRIS Consortium

Incorporated Research Institutions for Seismology

1200 New York Avenue, NW, Suite 800

Washington, DC 20008

From Galileo's telescope and Leeuwenhoek's microscope to the high technologies of the present day, many of the great discoveries in science have come from new tools that sharpen our images of nature. In just the last decade, the Hubble Space Telescope has extended the range of optical astronomy toward the outer limits of the Universe, revealing its turbulence in the wake of the Big Bang. Atomic-force microscopes are being used to map the topography of individual atoms on material surfaces, enabling rapid progress in nanotechnology. Medicine is advancing through computer-aided tomography and magnetic-resonance imaging of the human body. Multispectral cameras aboard satellites and multibeam sonars on ships are enhancing our views of the terrestrial surface over the land and beneath the sea.

In a similar way, the new tools of seismological imaging are revolutionizing the study of the solid Earth. Earthquakes and controlled sources such as underground explosions generate elastic waves that encode an immense amount of information about the Earth through which they propagate. This illumination can be captured on arrays of seismic sensors and digitally processed into three-dimensional images of Earth structure and moving pictures of earthquake ruptures. Seismology thus gives geoscientists the eyes to observe fundamental processes within the darkened depths of the planetary interior.

Exploring the Earth beneath its surface is the primary mission of the Incorporated Research Institutions for Seismology. The IRIS consortium comprises nearly 100 universities and research organizations engaged in four major programs: (1) The Global Seismic Network (GSN), a worldwide network of xxx broadband seismometers for earthquake studies and seismic investigations of deep Earth structure. (2) The PASSCAL Program of portable instruments for deployment by individual investigators for both active and passive source experiments in regions of special interest. (3) The Data Management System, a organized facility for both archiving and distributed the large data volumes collected by IRIS instruments, and (4) An Education and Outreach Program to bring seismological results to educators and the public. This proposal requests funds from the National Science Foundation to continue and enhance these IRIS operations for the period from July 1, 2001, to June 30, 2006.

Despite the richness of the seismological data sets, seismology alone cannot solve the outstanding problems of Earth science. Some of the most fundamental issues concern the dynamics of highly complex geosystems, which involve processes spanning spatial scales from millimeters to thousands of kilometers and temporal scales from fractions of a second to billions of years. The study of these geosystems requires a multidisciplinary approach.

[Paragraph illustrating major areas of inquiry, from the global systems of mantle convection and the core dynamo to local processes associated with magmatism, earthquakes, and natural resources, emphasizing the confluence of scientific issues with practical problems and concluding with IRIS as an IT organization for all of Earth science.]

The mission of IRIS extends beyond the operation and management of seismological facilities in several other ways. [Education and outreach, etc.]

USArray is a planned facility to systematically map the deep structure of the U.S. continent using a transportable array of broadband instruments over a 5 to 8 year period. It will be funded through the MRE program of NSF as part of the EARTHSCOPE initiative (which also includes the San Andreas Fault Observatory at Depth (SAFOD) and the Plate Boundary Observatory (PBO)). The USArray part of EARTHSCOPE will be operated by IRIS and USArray data will be archived at the IRIS Data Management Center (DMC). Note, however, that although IRIS will be key to the success of USArray, the MRE funding will not support the IRIS core programs. This proposal (submitted, as in previous years, to the MRI program) is intended to keep these facilities operating.

The Advanced National Seismic System (ANSS) is an initiative sponsored by the U.S. Geological Survey and operators of local seismic networks to permanently upgrade and improve U.S. capabilities to monitor local and regional earthquake activity, especially the strong motions associated with large events. The goals and strategy of this proposed program are different from those of USArray, which focuses more on mapping Earth structure through portable instrument deployments. The ANSS networks will not be operated by IRIS, although IRIS may have a role in coordinating data access.

The International Monitoring System (IMS) is [brief description]. IRIS contributes xxx stations to the IMS. IRIS has no direct role in CTBT monitoring research but works to ensure the open and free exchange of data that makes such research possible. The IRIS DMS serves as a model to coordinate international cooperation and to safeguard the culture of free and open data exchange.

[Brief description of structure of proposal]

FOREWORD i

OVERVIEW ii

TABLE OF CONTENTS iv

SECTION ONE

• Motivating Scientific Rationale 1

• The Resolution Revolution x

• The Value of Coverage x

• Big Questions x

• The Role of the Facilities x

• Financial History and Overview (2 pages) x

• Introduction x

• Continental Lithosphere x

• Plate Tectonic System x

• Deep Earth x

• Earthquakes x

• Education x

• Program Management x

• Consortium Activities x

• The Global Seismographic Network x

• The PASSCAL Program x

• Education and Outreach x

• The Data Management System x

SECTION ONE

The Earth is a complicated system and important Earth processes span a wide range of spatial and temporal scales. Seismology has played a key role in unraveling these processes owing to its ability to image and resolve Earth’s interior with greater clarity than other geophysical and geological methods. Detailed seismographic studies are now beginning to show us a fabric within the Earth’s interior that previously lay hidden within the large scales of earlier studies. Without doubt, however, important geological processes remain undiscovered beyond the resolution of our current data sets.

When high-resolution data sets become available, we often make new discoveries. In the past few years, geological and geophysical studies (many based on data generated and compiled with IRIS facilities) have led to some surprising and important results. For example, PASSCAL experiments in the United States (Dueker and Sheehan, 1997; Li et al., 1998) have imaged small-scale topography on the 410 and 660-km discontinuities that is hard to reconcile with simple thermal models. Waveform modeling of core-diffracted seismic phases has led to the discovery of ultra-low velocity zones just above the core-mantle boundary that are likely regions of partial melt (Garnero and Helmberger, 1996; Williams and Garnero, 1996). Recent seismic tomography results indicate a decorrelation between compressional and shear anomalies in the lower mantle (Su and Dziewonski, 19xx), suggesting that variations in mantle chemistry are affecting seismic velocities in this region. Analyses of shallow reflection seismic data have led to the discovery of blind-thrust faults below Los Angeles (Shaw and Shearer, 1999) which may pose a greater hazard than the better known San Andreas Fault.

Plate tectonics has proven very successful in explaining the large-scale features of Earth’s surface. However, processes at very small scales controls much of what is happening at the larger scales and the physics of these processes is not well understood. Numerical modeling of mantle convection has been unsuccessful in yielding plate tectonics without imposing artificial rheologies or boundary conditions. Faults in the crust apparently slip at much lower values of shear stress than laboratory experiments would indicate. Resolving this discrepancy is crucial to understanding why earthquakes occur and how crustal deformation fields evolve.

Seismology plays an important role in connecting surface geological observations to deeper Earth structure. Earth scientists appreciate that the solid earth is a system in which it is probable that related physical processes explain phenomena deep in the earth as well as complexity at sub-plate scales. Continued progress will require data with higher and higher resolution and will also need the perspective provided by long term monitoring efforts.

For most investigations, seismology has the potential to provide the best detail and thus definitive image of the Earth’s interior structure. Although other geophysical measurements also provide important information, the power of seismic techniques prevail in academic studies of lithospheric and deep Earth structure, as well as in oil exploration. In recent years, seismology has also come to the forefront in studies of environmental problems, water resources, and natural hazards. As we seek answers to the expanding array of societal questions, the demand for higher resolution data increases.

When the National Science Foundation was first founded 50 years ago, we were just beginning to realize that the deep structure of the continents and the oceans were fundamentally different. Whether for research, exploration, or education, nearly all applications of seismology now require detailed, definitive images. In technical terms, the push continues for higher and higher resolution, regardless of the scale of the investigation. Higher resolution requires more data, and the gathering of more data requires the deployment of more seismic instruments.

IRIS arose out of the need to acquire high-quality seismological data on a global scale and investigate structures and processes at a variety of scales. Thanks to three decades of efforts catalyzed by the availability of IRIS facilities, seismologists have produced results that permit geological features exposed at Earth’s surface to be traced to great depth. For example, slabs have now been imaged descending into the mid mantle in some regions and the large-scale structure near the core mantle boundary appears related to areas of past and current subduction. The deep structure of hot-spot related plumes is beginning to be imaged by tomography studies (XXX reference). Individual subduction zones can now be understood in terms of a detailed plate tectonic model that elucidates details of processes in a subduction zone that in turn reveals a terrane boundary bounded fault zones, thereby providing a seismotectonic analysis of a particular fault exposed at the surface.

Seismic results provide information not just to seismologists but to the entire geoscience community. Petrologists and volcanologists have a great deal of interest in seismic studies that map magmatic modification of the lithosphere; structural geologists and tectonophysicists rely heavily on seismic images of deep structure and earthquake data; sedimentary geologists need data on the deep structure and tectonic setting of basins; geomagnetists needs mor information about the core, and geodynamic modelers rely on tomographic images of the mantle as proxies for convection. Results based on data made possible by IRIS have provided much insight. However, we also face the dilemma that the high-resolution results presently available are so limited in geographic and depth extent that few universal features can be recognized. For example, recent seismic results from fundamental features such as mountain belts and rifts look more different than alike. This variability is intriguing and poses a great challenge for the future, because it suggests that there are sub-plate processes at work that we do not understand. Also, the glimpses of ties between processes at work in the lithosphere and features deep in the earth suggest a global model of the solid earth system exists. Plate tectonics has taught us to expect complexity but order in large scale processes that can only be resolved by scientific cooperation and integration of a variety of high quality data.

Finally, it is becoming clear that static views of Earth processes are not enough. A major effort in geophysics is general has been to progress from 2-D models and data sets to 3-D. Although a fully 3-D understanding of many processes is not yet available, we also need to progress to 4-D (time variable) data and analyses in many cases. For example, motions in the core can be monitored on human time scales and used to better understand the behavior of the Earth’s magnetic field; the magma movements under a volcano can be monitored and used to predict its behavior; and earthquake sequences can last for tens of years.

IRIS is posed to play a crucial role in the next revolution in the geosciences by providing the facilities needed to provide the high quality data needed if the Earth science community is to take the next big step in understanding our planet.

Each time an earthquake occurs, we (1) learn about new tectonic processes (such as Antarctica’s intraplate earthquake), and (2) we sample a new part of Earth’s interior as the waves produced by the earthquake travel to seismic stations around the world. Although our society views earthquakes as unusual events, on a global scale they occur often enough to allow a facility that monitors the Earth on a time-scale of decades to resolve in four-dimensions processes such as strain transfer between fault systems and possible earthquake triggering, magma migration under volcanoes, and the possible differential rotation of the inner core.

Thus, the value of seismic networks and data archives grows with time as a more complete picture of time dependent processes is built up. Even today, data from the old WWSSN instruments and other analog networks are often "mined" for their insights into historical earthquakes or to help illuminate structure along ray paths not yet sampled by more modern stations. The first images of the Farralon plate under North America (Grand, 19xx) were obtained from WWSSN data, as well as some of the first evidence for ultra-low velocity zones at the core-mantle boundary (Garnero and Helmberger, 1996). Researchers have traveled to old seismic stations in Alaska and Sweden to search for paper records that may contain valuable clues regarding inner core rotation. In the long term, the IRIS archives will prove even more valuable than those of the older stations as IRIS data are available in digital form over the Internet to researchers all over the world; they do not need to be hand digitized from microfilm at a number of different sites.

Unfortunately, there is a tendency for seismic networks to decay in the years following their initial installation as the excitement following their deployment wanes and their operation becomes more routine. Continued support can be problematic as funding agencies begin to look at new initiatives. Stations are abandoned as cost-saving measures, instruments that break are not quickly repaired, and the quality of the data stream begins to suffer. In the 1970s the WWSSN network began to deteriorate in this way. The declining data quality of the WWSSN, together with the recognition that new high-quality digital instruments were needed, was one of the major motivating factors behind the formation of IRIS and the new Global Seismic Network (GSN).

The GSN network is nearing its full complement of xxx stations and is collecting more data than ever before. The PASSCAL program is providing high-quality instruments to an unprecedented number of individual investigators. The IRIS DMC archives and distributes these seismic data to the community in standard formats, and has begun organizing additional geophysical data sets. The value of these programs to the geosciences will be felt for decades to come. The challenge now is to keep the programs going and to maintain a high level of data quality.

As discussed at greater length in section X, we are determined that complacency not begin to develop within the IRIS program. The quality of the data is continually monitored by the Harvard xxxxxx as well as the hundreds of individual scientists who use IRIS data. We intend to upgrade and replace our instruments as they become obsolete and to take advantage of emerging technologies (such as satellite telemetry and the Internet) for data collection. Finally, we will continually explore ways in which IRIS can operate more efficiently. (**mention merging and relocation of instrument centers, DMC study, or save to later section?***)

As evidenced by the past, the long-term accumulation of high-resolution data will undeniably lead to large and unanticipated discoveries. In many ways, this is the most exciting motivation for any scientific undertaking of this scale. However, it is easy to identify several important Earth science topics where it is likely that substantial progress will be facilitated by IRIS. These include:

Within the last ten years, we have discovered ultralow velocity patches along the core-mantle boundary using globally distributed stations (phases reflecting and grazing). Both targeted experiments (PASSCAL) and GSN coverage are needed to determine their true dimensions and characteristics. These regions may represent areas of partial melt that are hotspots on the core-mantle boundary and serve as the origin of mantle plumes.

As first observed in the 60s and 70s, the core-mantle boundary scatters waves. In the last five years, this phenomenon has been recognized as a ubiquitous feature of the core-mantle boundary. It might indicate small-scale structures and features at the core-mantle boundary, which in turn represent chemical and mechanical boundaries between Mg silicates of the lower mantle and iron alloy of the outer core.

We have also discovered anisotropy of the inner core. With more paths (discuss importance of duplicate paths & long-term monitoring), we will be able to determine if the inner core is homogeneous (single crystal) or whether it has a more complex structure and is perhaps convecting. Trends in the measured travel-times through the anisotropic core have provided evidence that the inner core is rotating at a different speed that the outer core (current rotation approx. 3 degree eastward)

The following paragraph needs a home!

[Include integration and information technology (DMS) here. DMS is an integrative data center. By combining and making available experiments done by different investigators, the DMS enables relational combinations of data sets to be developed and analyzed. Can develop synthesis by either region or tectonic type.]

[Enabling paragraph to promote concept of consortium and shared resources] Shared resources and consortium approach create an "enabling" function for scientists. Fifteen years ago, you would have to have been at one of 1/2 dozen research institutions to do cutting edge seismology, and you would have spent a considerable amount of your time maintaining instruments and data bases.

Now IRIS has standardized and made openly available state-of-the-art instrumentation. A PI can propose an experiment free of the constraints of maintaining a local technical capability for the instrumentation, and still anticipate a successful experiment. In addition, every scientist and student with access to the internet now has equal access to data from global, regional, and local networks around the world.

IRIS actively works to disseminate research findings and resources both within the scientific community (through the IRIS newsletter and workshop) and through the E&O program, which includes outreach publications, teacher workshops, undergraduate internships, and museum programs. (Injecting scientific)

There are no longer data acquisition boundaries to curiosity-driven research in seismology. Scientists are free to pursue inquiries outside their traditional areas of research. People are more fluid, thus opening up research opportunities for broader range of scientists and educators than have traditionally had access.

To address questions we have been asking requires sampling and data acquisition across the full range of spatial scales -- from dense deployments of PASSCAL instruments at spacings of meters to resolve the geometry of a specific fault or the flow path of a pollutant and microseismicity associated with earthquake nucleation and creep, to the 2,000 km global coverage spacing provided by the GSN for continuous tomographic models of the deep Earth structure, mantle convection, and global seismicity patterns.

[DMS] creates common data facility to archive and distribute data. The DMS also provides a common set of software tools that for a basis for analytical systems. Digital data, global communication systems, geosynchronous time, GPS, now allow for rapid earthquake location and characterization – a crucial element for the scientific response (aftershock deployments) and emergency response. Also safeguard the culture of free and open data exchange.

[E&O] makes the data available and digestible to a wide audience.

[PASSCAL] allows for custom experiment design for the problems at hand. Flexible station spacing and bandwidth allows innovative experiment design. Use of telemetry allows PASSCAL instruments to be deployed in flexible network configurations tuned to the specific problem and landscape. Stations can be deployed for longer periods of time, collecting more data with fewer people. Instantaneous access to data results in higher uptimes through more efficient network maintenance and quality control. Real-time analysis allows for experiment redesign and to exploit opportunities that arise in the field.

[GSN] provides a stable foundation. GSN is a backbone accumulating the long-term global data sets that will be used to determine the baseline against which anomalous processes and infrequent events can be recognized, measures, and understood. GSN also serves as the foundation data set for relating specific studies to global tectonics.

The Global Seismographic Network

References