On April 18, 1906, a significant earthquake sent seismic shockwaves throughout San Francisco. Though the Richter scale was not developed until 1935, most seismologists believe that this quake would have been between a 7.5 and a 8.2, the classifications for a "major" or a "great" earthquake respectively, though debate still lingers about what the most accurate magnitude might be.
The exact numbers of the damage incurred are also unknown. Rough estimates put the death toll around 3,000, perhaps more, while tens of thousands of others were rendered homeless. Eighty percent of the city was destroyed, mostly by catastrophic fires that followed the quake when ruptured gas lines ignited multiple fires that quickly spread through the city, destroying homes and businesses over 400 blocks. Breaks to water mains made fighting the fire, which raged on for three days, more difficult.
Methods for monitoring earthquakes were still in their earliest stages in 1906. The first seismographs used in the United States had been in place for fewer than 20 years. Despite the lack of modern technology, several geologists of the time studied the earthquake as best they could. Seismographs were still young. Some of these findings drastically shaped the course of seismology and the way we study earthquakes today.
The first of these scientists was Andrew Lawson, a geologist at the University of California, Berkeley. He wrote the official State Earthquake Investigation Commission report of the earthquake, what is now known as the Lawson Report. For two years, Lawson and his team studied the event intensely, recording maps, photographing the the damage and surveying of how the land moved after the quake. Among their results was the discovery that the type of land shaped how much of an effect the earthquake had, noting that strongest shaking occurred in soft, sedimentary soils.
This realization was significant for helping to shape building standards for quake-prone areas. Lawson's team reported that the most damaged buildings occurred on softer soil where the shaking was strongest. They also noted that the way different buildings were constructed had varying impacts from the earthquake.
The Lawson Report also greatly expanded knowledge of the San Andres Fault, previously named and discovered by Lawson in 1895. This fault line is a meeting of the Pacific and North American tectonic plates, spanning over 800 miles through California, mostly near the coast. It is a common location for many of California's earthquakes, including the deadly 1989 Loma Prieta earthquake and 2004's Parkfield earthquake. As the two major plates move against each other, they create significant seismic activity.
By walking the entire length of the fault, Lawson's team was able to study and record the way the fault moves when an earthquake occurs. This lead to H.F. Reid of Johns Hopkins University, a member of the commission, to develop the theory of elastic rebound. This theory was the first realization that plate shifting in the fault created earthquakes, and that earthquakes do not create the fault. This knowledge changed seismology significantly and led to our modern knowledge of earthquakes.
As much as Lawson's team discovered and learned, much is left unknown about earthquakes. More than 100 years later, the University of California, Berekley, is still looking to learn more.
Jennifer Strauss, External Relations Officer of the Berkeley Seismological Laboratory, explained that a team is currently working to create an early warning system for earthquakes. The goal is to be able to give people advanced warning.
"We want people to have time to get to safety, for important equipment to be protected," she said.
Earlier this month in California, Senate Bill 135 was introduced by Senator Padilla, which "would require the office, in collaboration with various entities, including the United States Geological Survey, to develop a comprehensive statewide earthquake early warning system in California."
When an earthquake occurs, there is a "foreshock" that shakes at a lower magnitude than the quake itself will. With the Earthquake Early Warning system, three different algorithms will run within the first few seconds that a foreshock is detected. The algorithms would try to determine the location and magnitude of the earthquake itself based on this information. The system would then transmit a warning to the public, via television, radio, internet and cell phone alerts.
The team, consisting of members of the Berkeley staff and other universities and institutions, continues to work towards advancing this program and taking it to the public. It is hoped that the passing of SB-135 will provide crucial funding and support to get the system implemented.
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