Mapping Soft Soil Zones and Top-of-Bedrock beneath High-Traffic Areas in Honolulu Using 2D ReMi

Two-dimensional seismic refraction microtremor data were acquired, processed and interpreted for the Honolulu High-Capacity Transit Corridor Project — west of Honolulu, Oahu, Hawaii. The objective was to image the lateral and vertical extent of soft-soil conditions and determine the depth-to-bedrock. Approximately 4.28-line km (2.66 miles) of two-dimensional (2D) refraction microtremor (ReMi) data was acquired along 12 lines. Data were acquired along the Farrington and the Kamehameha Highways. Line locations were selected to obtain additional subsurface information between and below geotechnical borings. Results indicate that thick soft-soil conditions exist; and, that the basalt bedrock has considerable relief. The bedrock can be encountered as shallow as 1.5 m (5 ft), to as deep as 70 m (230 ft) in this area beneath the existing highways. An innovative application of 2D seismic testing successfully mapped the lateral and vertical variability of the soft-soils beneath areas with very high traffic volume, without interrupting vehicle flow.