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1969. The lengths of lines spanning the rupture zone are measured several times each week by a two-color laser distancemeasuring geodimeter capable of resolving length changes of about 0.04 inches over lines 3 to 5 miles long. Borehole volumetric strainmeters (dilatometers) also are being installed in the Parkfield area to provide continuous data having a sensitivity of about 1 part per billion over periods of a few hours. In addition, a number of wire strainmeters (creepmeters) span the surface trace of the San Andreas fault near Parkfield. These creepmeters can resolve a few fractions of an inch of anomalous fault slip and are well suited to detect premonitory slip of the magnitude that may have occurred in 1966.

Parkfield Earthquake
Prediction Scenarios and
Response Plans

The Geological Survey will attempt to issue a short-term warning (minutes to days) to government officials of the anticipated shock on the basis of precursory phenomena recorded by the prototype earthquake prediction network. Anomalous

conditions that would change the assessment of the earthquake's imminence and the action that would be taken by the Survey have been defined. A Survey planning document has been prepared describing the conditions that would trigger a Geologic Hazards Warning to the California Office of Emergency Services (OES). Responsibility for communicating these warnings to the public, to local governments, and to the press resides with OES.

A probabilistic approach to earthquake prediction has been adopted at Parkfield. The likelihood that the anticipated shock will occur in the near future increases as anomalous conditions (for example, increased seismicity) increase. Couching warnings in such a framework explicitly allows for the possibility that warnings will not be followed by the anticipated magnitude 6 shock in the near future. For example, warnings will take the form, "There is a 1 in 5 chance (0.22 probability) that the anticipated magnitude 6 shock will occur in the next 24 hours; the probability of the shock in the next 72 hours is at least 0.37." If any of the four observational networks now monitoring the Parkfield area detects an anomalous state with respect to the normal background condition of the networks, an alert will be indicated. If anomalous conditions are observed from more

than one network, the level of the alert will be increased according to formal rules. Preliminary alert-level criteria have been established for each network type. Seismic alert criteria are based on estimates of the probability that an earthquake is a foreshock to the anticipated magnitude 6 event. The criteria for the other three network types are based on how frequently anomalous conditions are expected to occur and subjective estimates of the probability that an anomalous condition will precede a magnitude 6 shock at Parkfield. Tables 1 and 2 describe the responses triggered by the different alert levels and the types of data provided by the networks that have triggered those alerts since June 1985.

Figure 3 shows the interrelationship between the alarm levels generated by the network and the operation of the alert systems. Specific conditions that trigger changes in the alert levels defined in table 2 include (1) potential foreshocks at the 1966 epicenter; (2) earthquakes anywhere within the Parkfield area; (3) creep-rate accelerations; (4) rapid changes in volumetric strain measured by borehole dilatometers or fluctuation in water-well levels; (5) changes in magnetic field differences; and (6) linelength changes between successive twocolor geodimeter measurements.

The operation of the Parkfield earthquake prediction network before and during the anticipated magnitude 6 earthquake will

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GEOLOGICAL SURVEY MISSIONS AND

PROGRAMS

MISSIONS

BUDGET

The U.S. Geological Survey was established by an Act of Congress on March 3, 1879, to answer the need for a permanent agency at the Federal level to conduct investigations into the "geological structure, mineral resources, and products of the national domain." Although a number of laws and executive orders have expanded and modified the scope of the bureau's responsibilities over its 107-year history, the Geological Survey has remained principally a scientific and technical agency rather than a developmental or regulatory one. Today, the Geological Survey is mandated to assess onshore and offshore energy and mineral resources; to provide information to help society mitigate the impact of floods, earthquakes, landslides, volcanoes, and droughts; to monitor the Nation's ground- and surfacewater supplies; to assess the quality of the Nation's water resources; and to provide mapped information on the Nation's lands and land use. The Geological Survey is the PERSONNEL principal source of scientific and technical expertise in the earth sciences within the Department of the Interior and the Federal Government.

In fiscal year 1986, the Geological Survey had obligational authority for $600.8 million, $412.7 million of which came from direct appropriations; $8.6 million came from estimated receipts from map sales, and $188.2 million came from reimbursement. The Survey was reimbursed for work performed for other agencies whose needs for earth-science expertise complement Survey program objectives. Work done for State, county, and municipal agencies is almost always done on a cost-sharing basis.

ORGANIZATION

The Geological Survey is headquartered in Reston, Va. Its scientific programs are administered through the Geologic, Water Resources, and National Mapping Divisions, supported by the Administrative and Information Systems Divisions. The Survey conducts its functions through an extensive organization of field offices located throughout the 50 States and Puerto Rico. At the national level, the functions of the Survey are coordinated through Assistant Directors for Administration, Programs, Research, Information Systems, Intergovernmental Affairs, Engineering Geology, and Management Applications.

Most of the appropriations and reimbursements received by the Survey in fiscal year 1986 are distributed through budget activities that roughly correspond to its geologic, hydrologic, mapping, and administrative areas of responsibility. Budget tables appear on page 143.

At the end of fiscal year 1986, the Geological Survey had 8,062 permanent fulltime employees. The Survey's diversified earth-science research programs and services are reflected in its workforce, which is composed of personnel in more than 160 disciplines; more than half of that workforce possesses a Bachelor's or higher level degree. Almost half of the Survey's staff is made up of professional scientists, and approximately a quarter consists of technical specialists. Hydrologists, geologists, and cartographers predominate among the professional group, which includes members of more than 30 other disciplines, such as geophysics, chemistry, and engineering.

Permanent employees are supported by those other than full-time permanent employees, including many university students and faculty members as well as part-time employees. This relationship with the academic community has made the

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