Last Friday, July 5, 2019, 20:19 pm local time, the USGS Geological Survey recorded a second earthquake of magnitude 7.1 at a surface depth of 0.9 km northeast of the city of Los Angeles, south California.
A previous tremor of magnitude 6.4 degrees and with the epicenter to 11 km of depth in the same area of Searles valley was perceived the previous day coinciding with the celebrations of the Independence Day in United States, for this reason already called by many “the earthquake of the July 4th”.
The tremor was felt intensely in Las Vegas, Nevada, as well as in the Mexican city of Tijuana, on the border with the United States.
They have been considered as the two most powerful seismic movements of the last two decades that have hit the state of California.
They have not caused human victims, but some slight injuries and material damage. Experts fear in the coming days possible replicas of greater or lesser intensity as the hundreds detected in the last hours.
Although the epicenter of the earthquake was detected in an unfrequented rural and desert area, the nearby city of Ridgecrest, where 29,000 people live and located 250 kilometers north of Los Angeles, received the most damage; some falls of rocks on the roads, interruption in the electricity supply, water and gas leaks, fires in some buildings and difficulty in telecommunications and transport.
” We feel that damage has been recorded, but we do not yet know to what extent, ” Dern County Fire Chief David Witt told to a news conference on Saturday. Later he updated that approximately 1,800 people had run out of electricity in the area and that only some of them had suffered minor minor injuries such as cuts or bruises.
” No one was caught, there are no big landslides that we know of. But we are looking for, “he added.
Ridgecrest Mayor Peggy Breeden told the Reuters news agency: “We have fires, we have gas leaks, we have injuries, we have people without electricity. We are dealing with it the best we can. “
The tremor was felt by millions of people from Los Angeles, Las Vegas to Tijuana.
In Los Angeles, the Fire Department reported that there had been no deaths or injuries, only interruptions in the supply of electricity and some downed power lines, no significant infrastructure damage.
On Hollywood Boulevard in Los Angeles the earthquake was felt intensely, the traffic lights and cars began to move for 10 to 15 seconds. After the shake, the traffic continued normally, according to some witnesses.
In Las Vegas some basketball games of the NBA Summer League were canceled, however the baseball game between the Los Angeles Dodgers and the San Diego Padres already started when the earthquake occurred was not interrupted, even the organist Dieter Ruehle responsible for the music at Dodger Stadium improvised the song “I Feel the Earth Move” immediately after the tremor.
The governor of California, Gavin Newsom, in a statement asked President Donald Trump to declare the area a state of emergency so that federal aid could reach the affected areas more effectively and quickly.
According to the experts, possible replicas of equal or greater magnitude to these precedents of the 4th and 5th of July are not excluded.
Lucy Jones, an expert seismologist at the California Institute of Technology, said the two earthquakes are part of the same Searles Valley sequence. He added that the probability of a replica is more intense than the previous earthquake is 1 in 20 and that the fact that there has been a large earthquake does not reduce the possibility of an equal or greater magnitude.
«The M6.4 was a foreshock. This was an M7.1 with the same fault as the Searles Valley sequence. This is part of the same sequence, “said Lucy Jones of the California Institute of Technology, Caltech, an authority and seismology expert.
“Yes, we estimate that there is a 1 to 10 chance that Searles Valley sees another M7. That’s a 9 to 10 chance that the M7.1 tonight was the biggest. “
These last two earthquakes have been the most powerful registered in the last 20 years in the State of California.
Although the epicenter did not occur in the San Andreas fault, the fear and restlessness that is causing this renewed seismic activity in the area is evident and very worrying.
Even more so when the experts and the authorities are warning for some time about the possible devastating consequences of the so-called “The Big One“, the hypothetical destructive earthquake that will originate in the San Andreas Fault.
The most tragic and most recent earthquake occurred in Northridge in 1994, a magnitude 6.7 earthquake with an epicenter in the San Fernando Valley, near the metropolitan area of Los Angeles that caused 57 deaths, thousands of injuries and extensive material damage to highways. and buildings, so it is understandable the concern that has caused this recent seismic activation in the area.
Fortunately, these earthquakes in the Searles Valley located their epicenter in areas of the deserted Mojave depopulated northeast of Los Angeles far from urban areas.
THE FEARED AND EACH TIME CLOSER “BIG ONE”
” The Big One” as it is known is a mega-earthquake that according to experts will occur in the next few years in the San Andreas fault. With a magnitude greater than 8 and lasting between 3 and 5 minutes, it is predicted to be impressive and catastrophic.
The consequences will be devastating causing a tsunami continued for at least 12 hours and with a volume of water 2 times greater than the one that affected Chile in 2010.
According to forecasts, Palm Springs will be the city in which the epicenter will be located. The mega-earthquake will affect the entire state of California being the city of Los Angeles one of the most affected.
Plate tectonics causes a continuous movement of the land mass causing continental drift, which in turn causes the collision between the plates.
Shocks, frictions and joints between the boundaries of the plates produce faults or cracks like the one of San Andreas and in active faults as it is the case, the surrounding terrain moves producing earthquakes like those of the past 4 and 5 of July and their aftershocks.
In this case, while the areas surrounding the San Andreas Fault, such as Los Angeles, San Diego and Santa Bárbara, move slowly to the north and other areas such as Sacramento, San Andreas and the Mojave Desert move south, the area that contains the San Andreas fault of about 800 miles from Monterey to Mexico is blocked without the possibility of movement accumulating a great tension that sooner or later will generate a seismic movement of great magnitude.
It is assumed therefore that inevitably in the day of The Big One the fault of San Andreas will have to break, fracture and separate to release the seismic tension accumulated in its interior.
The mega-earthquake of the San Andreas fault is very feared because its effects are calculated to be perceive immediately, suddenly and devastatingly. The cracks that will open are calculated to reach several meters. It is enough to remember the earthquake of magnitude 7.8 of 1906 that devastated San Francisco; in the county of Marin, in the town of Point Reyes, the land was separated by the San Andreas up to 18 feet.
According to experts, large earthquakes such as those on 4 and 5 July do not alleviate the seismic stress accumulated in the San Andreas Fault or delay the inevitable Big One day. On the contrary, a high intensity earthquake increases the risk of future earthquakes in little time and the so-called “replicas”, which are sequences of earthquakes related to each other.
Indeed, after the two major earthquakes that have recently occurred, hundreds of aftershocks have followed in the area surrounding the epicenter in the Mojave Desert, near the city of Ridgecrest.
It can not be foreseen in what exact area of the fault will originate The Big One and what intensity it will have although it is estimated that it can reach 8.2, but it will inevitably happen and will have catastrophic consequences.
Front cover photo: https://twitter.com/Rex_Emerson/status/1146862954148585473