CURRENT GEOLOGIC MAPPING IN THE GREATER SEATTLE AREA, WASHINGTON STATE

Geologic mapping in urban areas of the Pacific Northwest is enjoying a renaissance, driven by local public agencies appreciating the need for updated geologic information to support hazard assessments and the geoscience community’s interest in a broad range of unsolved scientific questions in this region. One such effort is focused on the central Puget Lowland of Washington State, where the Seattle-Area Geologic Mapping Project at the University of Washington (http://depts.washington.edu/sgmp) has developed a collaborative project with the US Geological Survey to produce a series of new maps supported by field work; analytical studies; and a GIS-based relational database that efficiently stores, manipulates, and displays the vast amount of existing subsurface geologic data available throughout the greater Seattle area.

Subsurface data in urban areas, primarily in the form of geotechnical explorations, are abundant, but many are widely scattered in building and utility departments, transportation agencies, and private consulting firms. To date, geologic data from over 50,000 field explorations, exposures, and excavations in the greater Seattle area have been entered into the database. The data are being gathered from city building and utility departments, as well as county, state, and federal agencies. Data are entered into the database through customized GIS and database interfaces. The database contains “raw” data, including subsurface layers from boring logs, as well as fields for geologic interpretation and for the metadata on original source documents, original scale, and data quality.

Geologic maps using these data are currently in preparation, review, and production by the USGS for the entire city of Seattle and several surrounding areas. They represent a new level of mapping for the region with a variety of direct and derivative byproducts. Partnerships have been formed with a number of local public agencies both to acquire the raw data from geologic and geotechnical studies and to return the populated database and GIS interface to those agencies and the public. Through these partnerships, the information is becoming available to engineers, planners, and the public to identify where non-proprietary geologic data can be reviewed to improve subsequent investigations and to improve hazard mapping.