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SAN FRANCISCO — A new account for clash faults could help oneself explain mysterious defect lines that have mystified geologists for 10 . The newfangled explanation could explicate everything from the quake - prone faults of Southern California to dynamic crust beneath the snow - crest heyday of K2 in the Himalayas .
The theory is deceptively simple : When two faults collide , instead of one ruin past another , they may just unify , like a zipper zipping up , say John Platt , a geologist at the University of Southern California in Los Angeles , here at the annual meeting of the American Geophysical Union . [ Photo Journal : The Gorgeous San Andreas Fault ]
This segment of the San Andreas Fault, in Palmdale, California, lies about 60 miles (100 km) northwest of Los Angeles. The image was captured from the Space Shuttle Endeavor on Feb. 11, 2000.
" It may lick some long - stand and intractable problems come to the timing and displacement reaction on faults , " Platt state in the presentment .
foreign rocks
Platt and his confrere Cees Passchier , a technophysicist at the University of Mainz in Germany , were look at a foreign rock’n’roll geological formation called Cap de Creus in Spain . To a geologist ’s eyes , the rocks make no sense , with rocks on one side of the defect showing augury of shear in one focussing and those on the other side have the diametric shear orientation . commonly , the instruction of movement reveal in the rock’n’roll should be the same on either side of the fault . ( At Cap de Creus , the textural lines in the rocks make a " V " shape around the fault , while normally that texture would wait more like diagonal lines that cross the demerit . )
Passchier " show it to me in the field ; it just blow my mind . I thought ' There ’s just no way , it ’s whole impossible , ' " Platt tell Live Science .
But see Cap de Creus acquire him thinking about another fault junction nigher to home . About 60 miles ( 97 kilometers ) compass north of Los Angeles , in a small mountain town shout out Gorman , theSan Andreas Faultcollides with the Garlock Fault , which then head east into the Mojave Desert . ( The San Andreas Fault formed 30 million age ago when the North American and Pacific plates first meet and began to slew past each other , forming astrike - slip faultthat snake about 800 miles ( 1,287 km ) north along the California coast , from the Salton Sea to the Mendocino Coast . )
Based on traditional conceptions of faults , either the Garlock Fault should have cut down through the San Andreas Fault and deactivated it , or frailty versa . But the San Andreas Fault has about 150 miles ( 241 km ) of slip between either side , mean that volcanic rocks inPinnacles National Parkmatch those much farther in the south , in Los Angeles County . The Garlock Fault , by direct contrast , has 18 miles ( 30 klick ) of gaffe .
So if the San Andreas Fault had cut the Garlock Fault , it should have countervail the Garlock Fault by a banging 150 mile ( 241 km ) , deactivating it , and if the Garlock Fault had cut the San Andreas Fault , it would have squeeze the San Andreas over by 18 land mile ( 30 kilometre ) . And yet clearly , neither has fall out , and no one really thought to enquire why .
" It ’s a classic paradox , " Platt say .
Simple solution
So Platt wondered whether the two simply join . In that instance , the slip between the two would be added ( in this case , because the two slip in diametric directions , the berth of one would be subtracted from the other . ) The faulting , in core , would act more like a zipper being close .
When he and his workfellow thought about it , the construct of " zipper faults " could explain many of exceedingly confusing spots around the earth . All told , the squad came up with about 27 different versions of the zip defect , depending on whether the junctions are " unzipping " or " zipping , " and whether the fault collisions include dextral , sinistral or bomber faults . ( In this instance , sinistral means leftward , while dextral means rightward . )
For instance , the Altyn - Tagh and Karakoram geological fault , which sit down on the Tibetan plateau , have long inspired furious public debate among shell tectonics researchers , because rocks on either side of each geological fault make the resulting slip difficult to reconcile . For instance , some have suggested that theKarakoram Faultmoved as much as 30 mm per class , whereas others said the shift motivate just 3 mm a twelvemonth . [ The World ’s grandiloquent Mountains ]
" You would n’t believe the arguments about those faults , " Platt order .
scientist could go to the region to see if zippering could explain the confusing careen , though it ’s hard to survey in the region because of the baleful terrain , he say .
Platt noted that earlier geologists have even used the countersign " zipper " to explain a few other shift , such as one in theAlps , but they never connect the battery-acid to create a comprehensive theory .
Simple but potent
One way to test the idea is to set sophisticatedglobal lay system(GPS ) twist around the faults to measure how much they are move at a given time and see if they match with propose slip based on the zipper model , he said . At the San Andreas / Garlock Fault intersection , the slip rate northward of the junction should be less than that Dixieland of the intersection , if his zippering possibility is correct .
" I really wish it , the estimation , " said Ivanka Mitrovic , a geodynamics research worker at the National History Museum and the University of Vienna in Austria , who was not involved in the discipline but who attended the talk . The idea is " very simple , but it ’s that dewy-eyed brilliance , " she said .
If the opinion of zipper fault proves lawful , it " would serve link opposing persuasion , " Mitrovic told Live Science .
