CREATING MULTIPLE TECHNICAL DERIVATIVES FROM DIGITAL GEOLOGIC MAPS

The Kentucky Geological Survey (KGS) is collaborating with technical geological map users to develop audience-focused technical derivative maps from recently completed digital Quaternary geologic maps. The KGS continues to map Quaternary deposits and landforms in western Kentucky as a part of the USGS STATEMAP Program. The purpose of this study is to characterize the three-dimensional lithologic architecture of unconsolidated deposits in the Ohio River Valley and develop digital geologic maps which can be used to generate multiple derivative maps that support geohazard, geotechnical, land-use planning, and hydrologic investigations. KGS has recently completed digital conversion of 1:24,000-scale geologic maps for the entire state. These digital maps typically focus on bedrock features and generalize unconsolidated deposits, and are used as a starting point for the Quaternary mapping. The current Quaternary mapping efforts use traditional geological mapping of unconsolidated sediments and landforms. Mappers incorporate landform delineation, shallow soil probes, cores, measured sections, seismic profiles, and geochronology into their data collection and interpretation effort. The KGS is making extensive use of digital technology to collect, process, store, and deliver the new mapping data.

A qualitative rubric, represented by a table of values related to geologic unit age and origin, was applied to Quaternary geologic map units to produce a liquefaction potential derivative map. This map shows the relative susceptibility of map areas to liquefaction during a major seismic event.

Seismic shear-wave velocity and depth to bedrock were integrated with Quaternary geologic map units to produce a NEHRP soil classification map. This map shows the relative susceptibility of map areas to ground motion amplification during a seismic event.

Hydrologic data and unit thicness were integrated with the Quaternary geologic map units to develop an unconsolidated aquifer map. This map shows the extent and thickness of potentially useful subsurface water supplies.