A06_Specifications_-_Seismic_Refraction_Unit.docx

SALIENT CHARACTERISTICS

Requirements for a 24-channel seismograph and associated equipment Seismic Refraction Tomography is a widely used geophysical technique that allows for imaging of the subsurface using seismic waves generated on the surface of the earth. The Oklahoma Texas Water Science Center (OTWSC) currently has a need to map out deep paleochannels and potential fault lines at depths up to 600 feet below the surface of the earth. The acquisition of a 24-channel seismograph, geophones, cables, software and a propelled energy generator would allow the OTWSC to successfully acquire the data required to fulfill their mission. The seismic equipment and associated software listed below would allow the OTWSC to collect seismic refraction and reflection data that will complement other geophysical methods used in the field. The ability to use complementary methods to clearly map out the subsurface quickly and efficiently will result in higher quality data, less time spent in the field, ultimately saving time and money for the center.

Item 1: One 24-Channel Seismograph

· Must collect ultra-high resolution, 24 bit data required for 2D, 3D and tomography surveys

· Must have frequency range from 1.75Hz to 20kHz

· Must have an input impedance of 20 kOhm, 0.02 µf and maximum input signal of 2.8 V PP, 0 db

· Must have a stacking trigger accuracy of no less than 1/32 of the sampling interval

· Must have pre-amp gains of 24 and 36 db

· Must be water-proof, dust proof, shock proof and able to withstand extreme temperatures

· Must be expandable/linkable to increase the number of channels available

· Must weigh less than 10 pounds

· Must be able to synch with a GPS unit

· Must connect to a laptop

· Must operate with a 12v battery, using no more than 0.5W per channel during data acquisition

· Must have user selectable criteria for seismic events

· Must use hammer switches

· Must be made in the USA

Item 2: Twenty-four, 4.5 Hz Vertical Geophones and cables:

· 4.5 Hz Geophone must have a clean response up to 160Hz with 0.6V/in/second sensitivity

· Must be housed in a waterproof case

· Must have a 7cm spike and 1 meter long cable lead with one D-loop terminating with a pair of Mueller clip connectors (RTC)

Item 3: Twenty-four, 14 Hz Vertical Geophones and cables

· 4.5 Hz Geophone must have a clean response up to 240Hz with 0.5V/in/second sensitivity

· Must be housed in a waterproof case

· Must have a 7cm spike and 1 meter long cable lead with one D-loop terminating with a pair of Mueller clip connectors (RTC)

Item 4: Geophone spread cable

· Must have 24 wire-wrap takeouts spaced at equal intervals of 25 meters and 10 meters of lead cable terminated with one 61-socket connector on each end

Item 5: Three Free standing reels

· Free standing reel with carrying and turning handles must be able to accommodate 250 meters of smooth 8 mm diameter cable and up to 200 meters of cable with takeouts.

· Must not weigh more than 55 pounds when loaded with 250 meters of 8 mm diameter cable

Item 6: Twenty-four tripod bases

· Tripod base with tipped corners must accommodate 4.5Hz and 14 Hz geophones

Item 7: Two hammer Switches

· Hammer switch must be at least 15 feet in length

Item 8: Six trigger extension cables

· Must work with hammer switch or seismic timer

· Must be jacketed in an abrasion-resistant material, terminated in one 3-pin and one 3-socket connector

· Must be on hand reel

· Must be at least 300 feet long

Item 9: One Propelled Energy Generator

· Must have an hammer mass weight of 80 pounds

· Must have a hammer drop height of 14-17 inches

· Must have a cycle time of 3 to 5 seconds

· Must operate on 12 volts

· Must have an impact frequency band of 10 to 250 Hz

· Must be portable

· Must be mountable on a truck or utility vehicle

Item 10: Refraction Data Software

· Must operate on a Windows PC

· Must allow for up to 16,000 samples/trace, 512 traces/shot, 360 traces/interpretation and 65 shots/interpretation

· Must not have yearly maintenance fees

Item11: Surface Wave Data Processing Software

· Must operate on a Windows PC

· Must allow for multichannel analysis of surface waves, passive source microtremor data and horizontal to vertical spectral ratio data.

· Must not have yearly maintenance fees.