Teacher:In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.
Teacher: Now, understand the problem? Solve this instance: Southern California suffered a number of big earthquakes in the early 1900s, a pattern that prompted experts to declare the state an earthquake hazard. But new work shows some of the biggest temblors might have been caused by oil and gas production, not nature. The finding could ultimately change scientists’ predictions for earthquakes in the Los Angeles Basin, and how well they understand man-made, or “induced,” earthquakes around the country. 
  
 It is challenging enough for scientists to determine whether a modern-day quake is natural or induced, and even more so for one that occurred a hundred years ago. The tools they now use to measure earthquakes were not as sophisticated back then, and historic records are limited. So researchers Susan Hough and Morgan Page at the U.S. Geological Survey relied on a combination of old scientific surveys, crude instrumental data and newspaper accounts to piece together details of quakes in the early 20th century. “It’s not as precise as having seismic data, but that doesn’t mean it’s hopeless,” Hough says. 
  
 From those documents, they determined the quakes’ magnitudes, the location of their epicenters and other attributes. They eventually narrowed their investigation to the handful of big, damaging earthquakes that hit the region between 1900 and 1935, during the Los Angeles oil boom. (The largest temblors were the best-documented ones.) Hough and Page restricted their study to this time period because records were spotty prior to 1900, and other researchers had already looked for induced earthquakes in Los Angeles post-1935. The pair also dug through old state reports to get statistics on the oil and gas companies’ production volume, along with locations and depths of their wells. They then analyzed the industry and earthquake data to see if they could establish a connection between the two. 
  
 Hough and Page found that oil and gas production in the Los Angeles Basin may have caused four out of the five major earthquakes in the region during that time. The largest—the 1933 Long Beach earthquake—was magnitude 6.4, killed 120 people and caused $50 million in damage (in 1933 dollars). Their study, published today in the Bulletin of the Seismological Society of America, explains that the majority of those big earthquakes occurred close to oil wells, often soon after production began. In every case oil and gas companies had drilled the wells more than a thousand meters down, which was unusually deep for that time period. All of these factors, Hough says, provide evidence for a link between the earthquakes and oil and gas activity. But it is important to note the study does not prove any direct causation. “What they showed is that the conditions are such that the earthquakes could well have been triggered by oil pumping activity,” explains David Jackson, professor emeritus of seismology at the University of California, Los Angeles, who was not involved with the work. 
  
 Hough also says people should not directly compare the historic earthquakes in California with what is happening in places like Oklahoma and Texas now. In the Midwest today scientists say man-made quakes are largely triggered by injecting wastewater from oil and gas production down into deep disposal wells. That was not done in the early 1900s in California, however, so Hough says the temblors were likely caused just by taking oil and gas out of the ground. The California and Oklahoma quakes, she says, correspond to totally different mechanisms. In 2015 Oklahoma had nearly a thousand earthquakes of magnitude 3 or greater, up from an average of two per year between 1978 and 2008. 
  
 Hough’s study, however, could still have big implications. If oil and gas production did set off most of Los Angeles’s major earthquakes during the early 20th century, then seismologists may need to recalculate southern California’s rate of natural earthquakes. “It could be that some of the earthquakes we thought were natural were actually related to human activity,” Jackson says. “And it’s possible that we could have fewer earthquakes in the future than we've had in the past.” Obviously, that would be good news—especially in a city of about four million people. Hough has already begun investigating historic quakes in other parts of California as well as temblors that hit Los Angeles after 1935, so estimates could change even more. 
  
 The study may even tell seismologists something valuable about man-made quakes in places like Oklahoma. Scientists don’t know yet whether or not there’s an upper size limit on human-caused earthquakes. In Oklahoma the highest-magnitude earthquake (which hit in September) was 5.8. “People have suggested there might be a magnitude cap around 6, because of the size that's been observed in Oklahoma,” Hough explains. But if oil and gas production in Los Angeles set off the 6.4 Long Beach earthquake in 1933, Hough says it might suggest no upper limit—that induced quakes could have magnitudes as large as natural temblors. 
  
 Other seismologists agree this is important to figure out. “This study brings in the idea that oil and gas production activities can generate large-magnitude earthquakes,” explains Richard Allen, director of the Seismological Laboratory at the University of California, Berkeley, who also was not involved in the work. “We need to start recognizing that there's a growing body of evidence that oil and gas production activities can generate large-magnitude, damaging earthquakes. And that's something we should all take very seriously.” ||||| Early 20th Century Earthquakes May Have Been Caused By Calif. Oil Boom 
  
 Enlarge this image toggle caption T.J. Maher/AP T.J. Maher/AP 
  
 A new study suggests some Los Angeles-area earthquakes in the 1920s and 1930s could have been caused by the oil boom at the time. 
  
 The paper, scheduled to be published online Tuesday in the Bulletin of the Seismological Society of America, presents evidence that drilling around Los Angeles between 1915 and 1932 could have been associated with damaging earthquakes in the area, including the magnitude 6.4 Long Beach quake in 1933 that killed 120 people. 
  
 Although the modern practice of hydraulic fracturing has been tied to small man-made earthquakes, right off the bat, the study authors — Susan E. Hough and Morgan Page of the U.S. Geological Survey — make clear this is not a study to draw lessons from today. The authors write in the opening paragraph: 
  
 "Our results suggest that significant earthquakes in Southern California during the early twentieth century might have been associated with industry practices that are no longer employed (i.e., production without water reinjection), and do not necessarily imply a high likelihood of induced earthquakes at the present time." 
  
 As the Los Angeles Times points out, "Nowadays, water is carefully used to replace the pumped-out oil, which prevents land from sinking and also helps extract more oil," something that was not being done in the '20s and '30s in the oil fields of the Los Angeles basin. 
  
 Rather than a model for the present, the new paper is a lens through which to view the seismic past of Southern California, using scientific history. 
  
 The authors note that earthquake-sensing technology was neither as sensitive nor as widespread in the early 20th century as it is today. Most earthquakes in the Los Angeles basin in the first third of the century "caused light shaking reported by at most a few witnesses," they write. 
  
 A few witnesses are not the most reliable source of data, so Hough and Page limited themselves only to the 22 biggest, most widely felt earthquakes of the period, and compared those quakes to oil industry records from the time. 
  
 Of those earthquakes, they found 13 possibly or likely were associated with "oil production activities," including the drilling of deeper and deeper oil wells near hidden faults that are known to cause earthquakes. The authors based their findings on the best information available about when and where the earthquakes and drilling occurred and the kind of drilling being conducted. 
  
 Last year, Hough and Page published evidence that midcentury earthquakes in Oklahoma were triggered by the injection of wastewater during oil production in that part of the country. That historical finding was more relevant to today's oil production activities than the California data. The USGS announced earlier this year that pumping wastewater underground during oil production has caused parts of Oklahoma to be as seismically active as parts of California. 
  
 Hough and Page used a similar historical record analysis for the Oklahoma and California papers, but Thomas Heaton, director of the Earthquake Engineering Research Laboratory at California Institute of Technology, told NPR he thought the Oklahoma research was more convincing than the new California findings. 
  
 "There is a long history of earthquakes being triggered by increased fluid pressure," he wrote in an email after reviewing the new paper. "Although we don't understand [the association] very well, it's as close as our community gets to consensus that fluid induction triggers earthquakes." 
  
 "The tricky part of the equation in California is that earthquakes occur regularly without fluid injection," he wrote. 
  
 He did not go so far as to call into question the associations suggested by the paper — he thought it's certainly possible that oil drilling played a part in some or all of the earthquakes Hough and Page identified. But it's hard to be sure about the reason for any one quake. 
  
 "It would be no surprise to discover that some of our California earthquakes were triggered by oil production," Heaton wrote. "What would be surprising would be to discover that a team of scientists was able to present a compelling case that it had occurred in any particular example (e.g. 1933 Long Beach)." ||||| 7 p.m.: This article was updated with a quote from Caltech seismology professor Jean Paul Ampuero, details of a study published in February that identified earthquakes in the San Joaquin Valley in 2005 as having a significant chance of being induced by an oil company's injection of wastewater into the ground, and historical context of Huntington Beach as a major producer of oil in Southern California. |||||
Student:
The Los Angeles Basin has the reputation of being a dangerous place when it comes to earthquakes, but a new study suggests that reputation might be overstated. Two scientists with the US Geological Survey looked at the region's biggest quakes between 1900 and 1935 and found that we humans might be more to blame than natural fault lines, reports the Los Angeles Times. The reason? Oil production. In the Bulletin of the Seismological Society of America, researchers Susan Hough and Morgan Page show that big quakes of that era often occurred near oil wells not long after production started, reports Scientific American. That includes the magnitude 6.4 Long Beach quake of 1933 that killed 120 people, though the study merely shows a link, not proof the drilling was to blame. “It was kind of more of a Wild West industry back a hundred years ago, and the technology wasn’t as sophisticated,” says Hough. “People would just pump oil, and in some cases the ground would subside—fairly dramatically.” The scientists say their study shouldn't be used in the modern debate over fracking, which involves an entirely different process. They also note that today's oil-drilling practices are safer, including the use of water to replace oil, and thus their results "do not necessarily imply a high likelihood of induced earthquakes at the present time," per NPR. The LAT sees good and bad news: The study suggests the region isn't as prone to natural quakes as believed, but it also suggests that humans play a greater role in inducing them than thought. (Are the Sierras overdue for a big one?)