Seismic Refraction Services- Brochure

SPOTLIGHTGEOPHYSICAL SERVICESFor more information, contact Spotlight Geophysical Services at info@spotlightgeo.com on the web at www.spotlightgeo.comSeismic RefractionSeismic refraction is a geophysical method used to determine the seismiccompression-wave (P-wave) velocity structure of the subsurface. Seismic P-waves are generated on the surface, propagate through the soil and rock, and arerecorded by geophones at known distances from the source. Since P-waves arethe fastest portion of the seismicwave, they represent the first arriving energy ateach geophone (either direct or refracted). A seismograph is used to record thetravel-times of the first arriving energy, after which subsurface seismic P-wavevelocities can be derived. A tomographic inversion is used to develop a 2D P-wave velocity cross-section from the data. Seismic refraction data may beacquiredon landor inwatercoveredareas.? Non-invasively map stratigraphy and anomalousconditions? Applications include characterizing rippability anddredgeability, mapping the top-of-rock, and identifyingsoft/weakzones? Measurements made along survey lines or within asurvey grid to provide plan-view contour maps of top-of-rockorotherstratigraphicboundaries? Measurements can be made over water-covered areasusing an array of hydrophones and amarine source such asanairgun?Surveyproceduresoutlined inASTMD5777-000 50 100 150 200 250 300 350 400 450 500Distance (meters)-30-20-1001020El evat ion( met er s)I ncr easi ngHar dnessBasalt BasaltSedimentary Rock0 20 40 60 80 100 120 140 160 180 200 220Distance (feet)5060708090100El evat ion( feet )Top of Rock