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OverviewReMi is a new, proven seismic method for measuring in-situ shear-wave (S-wave) velocity profiles. It iseconomic both in terms of cost and time. Testing is performed at the surface using the same conventionalseismograph and vertical P-wave geophones used for refraction studies. The seismic source consists ofambient seismic "noise", or microtremors, which are constantly being generated by cultural and naturalnoise. Because conventional seismic equipment is used to record data, and ambient noise is used as aseismic source, the ReMi method is less costly, faster and more convenient than borehole methods andother surface seismic methods, such as SASW and MASW used to determine shear-wave profiles.Depending on the material properties of the subsurface, ReMi can determine shear wave velocities downto a minimum of 40 meters (130 feet) and a maximum of 100 meters (300 feet) depth.

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Shear-wave dispersion curve derived from ambient seismic noise, shown on the left, is picked andmodeled (right panel)

Optim LLC, 2002

rocedure. The data acquisition prsing conventional seismograph andeveals the shear-wave dispersion cuavefield transformation is then m

hear-wave velocity profile (Figureshe wavefield from the three separatuality control. The resolution of the

SSeeiissOOpptt®® RReeMMii™™ VVss3300 MMeetthhoodde PPrrooffiillee UUssiinngg RReeffrraaccttiioonn MMiiccrroottrreemmoorr ((RReeMMii))

ocedure consists of obtaining three 15-second seismic noise records P-wave geophones. The wavefield transformation of the noise recordrve (Figure, above left). The shear-wave dispersion curve from the

anually picked and the picks modeled to determine the subsurface, above right and on reverse side of this page). During data analysis,e noise records are manually picked and modeled for the purpose of final model is quantified based on the uncertainty in the picks.

ReMi can be used to obtain Vs profiles for:• Earthquake site response• Liquefaction analysis• Soil compaction control• Pavement evaluation• Mapping the subsurface and estimating the strength of subsurface

materials• Finding buried cultural features, such as dumps and piers

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For more information please contact:

Optim LLC1664 N. Virginia St

Seismology Lab, UNR-MS174Reno, NV 89557

USA

Phone: 775.894.6613 Fax: 775.784.1833. email: sales@optimsoftware.comwww.optimsoftware.com

Shear-wave profile determined by modelingthe dispersion picks. Note that the profilereconstructs the average velocity obtainedfrom shear-wave log. The above results arefrom the Newhall ROSRINE borehole site.

Key Benefits. The ReMi method offerssignificant advantages. In contrast to boreholemeasurements ReMi tests a much larger volumeof the subsurface. The results represent theaverage shear wave velocity over distances as faras 200 meters (600 feet). Because ReMi is non-invasive and non-destructive, and uses onlyambient noise as a seismic source, no permits arerequired for its use. ReMi seismic lines can bedeployed within road medians, at activeconstruction sites, or along highways, withouthaving to disturb work or traffic flow. Unlikeother seismic methods for determining shear wavevelocity, ReMi will use these ongoing activities asseismic sources. There is no need to close a streetor shut down work for the purpose of dataacquisition (Per picture below). And a ReMisurvey usually takes less than two hours, fromsetup through breakdown. These advantages sumto substantial savings in time and cost.

ReMi survey liusing regular Pgeophones

Recording SeisOpt ReMi data within a busystreet median, Milan, Italy. The recordingwas part of a software demonstrationconducted by Optim distributor CodevintecItaliana SRL. Because ReMi uses standardseismic recording equipment and ambientseismic noise as a source, no permits,traffic stops or even advance notice toauthorities were required. Since all thatwas needed was to make three 15-secondnoise recordings, Vs30 was determined inless than two hours, including setup andbreakdown of the seismic array. Picturedfrom the far right are Bill Honjas andDr. Satish Pullammanappallil (Optim LLC).Talking with Satish is a representative fromSeisOpt ReMi client Trento ProvinceGeological Survey.

StandardSeismographrecording ReMidata

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