Researchers used a granulose exposure of a tumble train merge with an eyewitness account to psychoanalyze the pestilent earthquake that struck San Francisco over 110 years ago .
In 1906 , a order of magnitude 7.9 earthquake fall San Francisco , destroying much of the urban center and vote out as many as 3,000 people , make it one of the virulent earthquakes in history . But it also gave birth to modern American quake science . Now , investigator are trying to realise the quake using cutting - edge proficiency — and some old documents .
“ It ’s important to understand how these larger quakes occurred so we can build safer buildings , ” explain Swetha Veeraraghavan , postdoctoral research associate in morphological computational science at Idaho National Laboratory . “ I recollect these types of eyewitness accounts really help with this . That ’s why I found the problem really nerveless . ”
Scientists have hear analyzing old images and eyewitness data before in order of magnitude to comfortably empathize the 1906 earthquake . Newer earthquake model free-base on more data and well computational power inspired the researchers to take another look at this famous image of a steam locomotor sitting on its side , taken shortly after the earthquake . They also examined a conductor ’s verbal description of the incident . The 1907 account show :
At Point Reyes Station at the school principal of Tomales Bay the 5:15 train for San Francisco was just ready . The conductor had just swing himself on when the train give a dandy lurch to the due east , follow by another to the west , which threw the whole power train on its side . The astounded director put down off as it went over , and at the batch of the falling chimneys and die windows of the place , he understood that it was the Temblor . The fireman turned to jump from the locomotive to the west when the return shock came . He then leaped to the east and adopt a Kodak he take a picture of the train here presented .
This might sound like meager information with which to remodel an quake , but it provides more information than you might think . The quake must have been herculean enough to cause the rocking and the tipping of the gearing . The team simplified the train ’s measurements into a tenacious orthogonal prism , and simplified the temblor to an up - and - down wafture apparent movement of the ground . They then used equality get up to describe a rocking orthogonal cylinder block in reaction to ground motion to calculate how big the undulation must have been to tilt the train .
Their analysis revealed that the minimal acceleration of the ground require to tip over the train would have been 4 meters per 2nd squared ( a picayune less than half the speedup of something falling to the Earth in a vacuum cleaner ) , while the minimum velocity would have been 0.5 meters per second , or around 1.6 feet per second .
On top of their psychoanalysis of the train tipping , the researchers were able to count on the localization of the temblor ’s hypocenter — the area where it actually occurred in the Earth below the epicenter on the aerofoil — based on the train ’s fix and conduct . While previous mannequin have suggested three locations for a hypocenter , this result reveals that only a hypocenter to the south of Point Reyes , California , would recreate the eastward , then westward tipping of the train , according to the paper publish in Seismological Research Letters . This leave a hypocenter offshore from San Francisco or near the California urban center of San Juan Bautista , confirming previous estimates .
The theme amount with uncertainty — for example , the researchers did n’t know how much the train count , and are using a simplified model to realize what go on .
Still , it confirm a organic structure of inquiry recreating this important quake . And it demonstrate more in the main that even in the absence of data , context of use clues , eyewitness accounts , and photographs can prove important for interpret earthquakes . Veeraraghavan said : “ mass have even used tombstones or statues that toppled over to estimate the flat coat motion . ”
EarthquakesHistoryPhysicsScience
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