Recent studies show that the oil boom was the actual cause of the Los Angeles based earthquakes that occurred in 1920-30. These series of earthquakes caused severe damage to people around. The magnitude was 6.4 which itself suggests how massive the destruction would have been. It is said that the drilling which took place on a large scale to find oil caused or triggered the earthquakes.
Back then technology was not so advanced and people had no clear idea of how the extraction of oil on a large scale could cause harm to the earth.
Now there are systems with the help of which we replace the oil extracted with same volume of water to prevent the earth from sinking in. However this was an unknown fact which could have saved many lives. There were repeated attempts to extract oil between 1915 and 1932. Most of the earthquakes have also occurred during this period. This is how the researchers concluded that excessive oil extraction without water replacement would have disturbed the equilibrium on the earth’s surface and triggered the seismic eruptions.
The studies however are based on the evidence a few witness have given. So this is not so reliable. Unfortunately there were no methods to record what actually happened during that time.