Serving Bay Area Geologic Hazard Information in Google Earth KML; a Network-Link Approach

James Luke Blair, Marco Ticci

USGS, 345 Middlefield Rd, Mail Stop 977, Menlo Park, CA 94025, United States

We present a method to convert and provide San Francisco Bay Area geologic map information in Google Earth KML format. Google Earth software is an interactive, virtual globe that can be effective for communicating important geologic information to public and scientific audiences. The USGS, CGS, and other groups have collected a wealth of geologic information in the Bay Area, but little has been done to organize and provide this data in a single location and viewing format. Static maps and associated GIS files are the common output of such mapping efforts, but these are not easily obtained or viewed by the general public.

Alternatively, geologic maps served in KML format can be downloaded from servers and viewed as overlays on the high-resolution static aerial imagery supplied by Google. Further, the software provides 3D terrain and the ability to search for a location by address or coordinates. Complex geologic maps result in large KML file sizes, which in turn, slows down network and CPU performance on the user∙s end. To provide for more efficiency, the method we present utilizes ESRI∙s ArcMap Model Builder software to automate the process of breaking a large GIS dataset into multiple KML tiles. An individual tile has the extent of a 7.5∙ USGS quadrangle and a file size small enough to be rapidly retrieved from a server and processed by Google Earth for viewing. A single KML file manages the visibility of all the tiles, retrieving only the necessary tile(s) to fill the field of view. We intend to use this method to present important geologic information such as bedrock geology and geologic hazard data, including liquefaction susceptibility, faults and fault zones, landslides, flood zones, and various shaking scenarios in the Bay Area.

URLs:
http://earthquake.usgs.gov/eqcenter/recenteqsww/catalogs/
http://earthquake.usgs.gov/regional/nca/virtualtour/