According to a new study, there is a possible link between oil production and a handful of damaging earthquakes that took place in the Los Angeles Basin during its oil boom in the early 20th century.
In particular, the 1920 Inglewood quake, the 1929 Whittier quake, the 1930 Santa Monica quake and the 1933 Long Beach earthquake may have been induced by oil production activities.
The finding is published in the Bulletin of the Seismological Society of America (BSSA). Researchers from the U.S. Geological Survey conducted the study.
Their study is one of the first to look at evidence for earthquakes caused by industry activity in the Los Angeles region before 1935.
Oil and gas production practices then were significantly different from today’s retrieval methods, the researchers note, so their findings “do not necessarily imply a high likelihood of induced earthquakes at the present time” in the L.A. Basin.
Other studies have concluded that there was no significant evidence for induced earthquakes in the area after 1935.
If researchers can confirm that some of these larger earthquakes such as the magnitude 6.4 Long Beach quake were human-caused, however, the findings could re-shape how seismologists calculate the rate of natural earthquake activity in the basin.
Los Angeles’ oil boom began in 1892 when oil was discovered near present-day Dodger Stadium, and L.A. Basin oil fields accounted for nearly 20% of the world’s total production of crude oil by 1923.
Despite this massive scale of production, it does not appear that induced earthquakes were common in the basin during the early 20th century.
Compiling the data to study this question, however, was a complicated task for Hough and Page. The researchers had to put together a list of all “felt” earthquake events in the L.A. Basin during the time period.
They used reports of shaking and property damage to calculate quake epicenters and magnitudes for earthquakes recorded by few if any seismometers.
By comparing the earthquake lists with the industry data, the researchers found several links between earthquakes and significant oil production activities that took place nearby and close to the same time as the quakes.
The precise location of the wells–whether they were close to a existing fault, for instance–along with well depth, appear to be important factors in whether an earthquake was induced.
The recent increase in human-caused earthquakes in the central United States and Canada make it important to understand the “full context” of how, where and why earthquakes are induced.
Citation: Hough S, et al. (2016). Potentially Induced Earthquakes in the Los Angeles Basin during the Early 20th Century. Bulletin of the Seismological Society of America, published online. DOI: 10.1785/0120160157.
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