2006 ITGUAM2006 ITGUAM

High Resolution Seismic Reflection High Resolution Seismic Reflection Investigations for Salt Dissolution Investigations for Salt Dissolution

Features in KansasFeatures in KansasBy By

Bob HenthorneBob Henthorne

What is Salt Dissolution?What is Salt Dissolution?

Removing the natural occurring salt layers Removing the natural occurring salt layers by the addition of fresh water.by the addition of fresh water.

Salt Dissolution Features in KansasSalt Dissolution Features in Kansas

Dissolution FrontDissolution Front

Salt Mine ActivitiesSalt Mine Activities

Oil Production Oil Production

Investigative Procedures Using High-Resolution Seismic Reflection Techniques

Investigative Procedures Using HighInvestigative Procedures Using High--Resolution Seismic Reflection TechniquesResolution Seismic Reflection Techniques

GoalGoal: delineate subsurface expressions of : delineate subsurface expressions of sinkholes or paleosinkholes or paleo--sinkholessinkholes

lateral extentlateral extentlocate and estimate size of void areaslocate and estimate size of void areasidentify bridging or slumpidentify bridging or slumppreferential growth directionspreferential growth directionsevidence for catastrophic failure evidence for catastrophic failure

Acquisition ParametersAcquisition Parameters

240-channel fixed spread2.5 m receiver station spacing

Two 40 Hz geophones5.0 m source station spacing

IVI Minivib25-250 HzThree 10 second sweeps

240-channel fixed spread2.5 m receiver station spacing

Two 40 Hz geophones5.0 m source station spacing

IVI Minivib25-250 HzThree 10 second sweeps

A 240-channel fixed spread allowed the recording unit to remain stationary while the source traversed

about 600 m of line.

A 240A 240A 240---channel fixed spread allowed the recording channel fixed spread allowed the recording channel fixed spread allowed the recording unit to remain stationary while the source traversed unit to remain stationary while the source traversed unit to remain stationary while the source traversed

about 600 m of line. about 600 m of line. about 600 m of line.

Receivers set in the base of the ditch with the source on the road shoulder

Receivers set in the base of the ditch with the Receivers set in the base of the ditch with the Receivers set in the base of the ditch with the source on the road shouldersource on the road shouldersource on the road shoulder

Approximately 10 Gigabytes of information is collected Approximately 10 Gigabytes of information is collected each day! Data is recorded unfiltered and unstacked.each day! Data is recorded unfiltered and unstacked.

High Resolution Seismic may have not been developed for High Resolution Seismic may have not been developed for finding sinkholes but the end result is the same.finding sinkholes but the end result is the same.

Kansas ProjectsKansas Projects

USUS--50 and Victory Road50 and Victory RoadUSUS--50 Hutchinson South Bypass50 Hutchinson South BypassUSUS--61 from Hutchinson to McPherson61 from Hutchinson to McPhersonII--70 Crawford and Witt Sinkholes70 Crawford and Witt SinkholesUSUS--54 Interchange Between Goddard and 54 Interchange Between Goddard and WichitaWichita

Looking Northwest from the Project Looking Northwest from the Project Site!Site!

II--70 Sinkholes70 Sinkholes

Salt Member is 270 feet thick and approx. 1300 feet below I-70

I-70 has dropped over 20 feet and continues to sink at over 4 inches per year.

I-70 Witt and Crawford Site

US-50 and K-61 Sites

Hutchinson Salt and Site Map and Victory Road Seismic LinesHutchinson Salt and Site Map Hutchinson Salt and Site Map

and Victory Road Seismic Linesand Victory Road Seismic Lines

Sinkhole on US 50 Near Hutchinson

Sinkhole on US 50 Near Hutchinson

Intersection US 50 and Victory Road1998 subsidence measured @ 30 cm below grade at centerline2001 subsidence measured @ 1 m below grade at centerline & 100 m in diameterAveraging about 20 cm/yrCentered a few 10s of meters to the NW

Two orthogonal, 1 km seismic profiles

Intersection US 50 and Victory Road1998 subsidence measured @ 30 cm below grade at centerline2001 subsidence measured @ 1 m below grade at centerline & 100 m in diameterAveraging about 20 cm/yrCentered a few 10s of meters to the NW

Two orthogonal, 1 km seismic profiles

Interpretation of West/East Profile

Interpretation of West/East Interpretation of West/East ProfileProfile

Several episodes of subsidenceSeveral episodes of subsidenceCharacterized by both normal and reverse type Characterized by both normal and reverse type faultsfaultsBridging and undercompacted (relative)Bridging and undercompacted (relative)

Interpreted North/South ProfileInterpreted North/South ProfileInterpreted North/South Profile

Constrained to small faultConstrained to small fault--defined defined areaareaAborted subsidence featureAborted subsidence featureDormant paleosinkholeDormant paleosinkhole

Subsidence will continue in this area for many years into the future, as it has for at least the last million years.

Growth to the west should be expected @ vertical rates of 10 to 20 cm/yr

Subsidence will continue in this area for many years into the future, as it has for at least the last million years.

Growth to the west should be expected @ vertical rates of 10 to 20 cm/yr

No compelling evidence to suggest risk of catastrophic subsidence

No compelling evidence to suggest risk of catastrophic subsidence

CONCLUSIONSCONCLUSIONS

USUS--50 South Hutchinson Bypass50 South Hutchinson Bypass

US 61 from Hutchinson to US 61 from Hutchinson to McPhersonMcPherson

26 miles of new 426 miles of new 4--lane highway across the lane highway across the solution front of the salt.solution front of the salt.

Approximate location of the Dissolution Front 8th Avenue Sinkhole Location

Approximate Location of the Dissolution Front

Any Questions?