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JSC Negotiates with A-V Corporation for Audiovisual Public Information - page 103 / 146

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Page 3

Examinationof the map shows that nearly all of the faults are confined

to two well-defined,curvilinearbelts which bear a close relationshipto oil

fields in the area. The associationis not accidental.All major fields shown

on the map are known or thought to be producingfrom sedimentsabove or peripheral

to salt domes. It is believedthat the formationof the domes and the faulting

are geneticallyrelated.

The faults are natural geologicfeaturesof antiquity.Seismic and drilling

data reveals that the faults persist to depths of thousandsof feet and show

clear indicationsof prehistoricmovementextendingover millions of years.

There is ample evidence for a prehistoricorigin of the faults, and for

prehistoricmotion along them. Unresolvedis the questionof why many faults

are so active today. It can be documentedthat natural movement on some faults

persisted into the very recent geologicpast, and is likely continuing.How-

ever, contemporyrates of movement along many faults, which range up to one-inch

per year, are in excess of what has occurred in the past.

If the contemporaryrates were characteristicof the recent past, there

should be many fault scarps over 30 feet. The largest fault on the map has a

scarp height of little more than three feet. The present anomalous rate of

movementmay be the result of human activity,specificallypetroleumand

ground water production.

The extractionof large quantitiesof water from shallow sedimentsbeneath

the city, and productionof petroleumfrom somewhatdeeper levels, has resulted

in large declines in fluid pressureswithin the subsurfacesediments.Inasmuch

as a link between fluid-pressuredeclinesand land-surfacesubsidenceis well

established,it may be that the withdrawalof water and petroleum products is

somehow triggeringor acceleratingmotion along preexistingfalts as well.

NASA-JSC

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