Dawn on Monday brought with it more than the sun to Los Angeles (L.A.): A 4.4 magnitude tremor rippled across the Los Angeles basin at 6.25 a.m. (PST), leaving buildings and the half-awake city shaking. Rolling down a 150-mile swath of land in Southern California, the quake was reportedly felt from San Fernando Valley to Long Beach. Though there have been no reports of damage to property or life, the early morning jolt has got seismologists wondering if it signaled the beginning of a fresh earthquake season in the Los Angeles basin.
Originally declared a 4.7 magnitude tremor, the earthquake was downgraded to 4.4 magnitude by the United States Geological Survey (USGS). With its epicenter located two miles from Encino and 15 miles west-northwest of the civic center in downtown L.A., the quake has been labelled the biggest in Southern California following the 5.5 magnitude quake that shook Chino Hills back in 2008. While seismologists expected quakes of a similar magnitude to hit the region each year, there has been an earthquake-drought in L.A. until Monday morning.
In the hours immediately after the quake there was a five percent probability, said USGS seismologist Lucy Jones, that the quake might have been a precursor to a bigger one. However, among the seven smaller quakes that followed, only two of them measured 2.5 or more on the Richter scale, while most of them hovered around 1.3 magnitude. Jones also said that the risk will go down to one percent by morning on Tuesday. According to Egill Hauksson, seismologist and veteran researcher at the California Institute of Technology (Caltech), it may be many months before it can be conclusively said that the Los Angeles basin was facing a new season of earthquakes. It takes a long period of time to determine if the rate of seismic activity has changed or not.
Another point being watched by seismologists is the unusual location from where the Monday quake originated: The Santa Monica Mountains. Since the beginning of recording of earthquakes this is the only tremblor, of a 4.4 magnitude, to originate from within the range, said Hauksson.
Stretching for 40 miles between L.A. and Ventura County, through Malibu in the west, the Santa Monica Mountains are an ancient rock formation. Comprising highly compacted and rigid blocks of rock, the range has always witnessed seismic activity clustered around its north or south, but never before within them, explained Hauksson at a press conference in Caltech. He added that the 4.4 magnitude tremor was within the expected range of quakes in Southern California and that it would mostly be studied to figure out how its unusual location corresponded with previous seismic activity.
Though the quake has been labelled a “typical” quake, its significance is not lost on the region, often dubbed as earthquake country. In a statement issued soon after the quake on Monday, L.A. Mayor Eric Garcetti said that it was a “reminder” to all families in the city to be prepared with water, food and other essential supplies along with a plan of action in case of a big tremor. He also confirmed that there was no damage recorded anywhere. However, L.A.’s many old concrete structures will come under scrutiny post-quake as they are the most susceptible to damage.
The state of California falls within the Pacific “Ring of Fire”, which has caused several decimating quakes including the tsunami-earthquake that devastated Japan in 2011. The state’s infrastructure and its people have for long braced for the “Big One”, which according to geologists is a certainty within the next 30 years. The quake on Monday morning is the biggest to strike L.A. after the one in 2008 and many are wondering if it has ushered another season of earthquakes. Till date, the biggest quakes recorded in the state are the 6.7 magnitude tremor recorded in L.A. in 1994 and the 6.9 magnitude quake in San Francisco in 1989. While the former resulted in an estimated $10 billion dollar damage and left at least 60 persons dead, the latter killed 67 persons.
By Aruna Iyer