What have been some of the biggest earthquakes in California to date?
California has been hit with many earthquakes over the last century, with Fort Tejon and San Francisco being the highest recorded at 7.9 on the Richter scale. The twelve largest earthquakes to hit California since the mid 1800s have ranged between 6.4 and 7.9 on the Richter scale.
Where is El Centro?
El Centro is the largest city in the Imperial Valley, located in the far corner of California, near San Diego.
The El Centro Earthquake
On May 18th, 1940, at around 9:30pm, an earthquake occurred near the international border, in the Imperial Valley in Southern California. It measured 6.9 on the Richter scale and affected both the United States and Mexico, with the city of El Centro being one of the hardest hit. The earthquake originated from the San Andreas fault line and was, in total, nineteen tremors. An hour or so after the first quake, a secondary quake followed. Whilst it was nowhere near as strong as the first, the secondary quake still caused disruption, damage and aftershocks. They continued to shake the earth throughout the night and into the next morning. Whilst the Imperial Valley had previously experienced strong earthquakes, the El Centro quake was the biggest recorded earthquake to date. It was also the first major earthquake to be recorded by strong-motion accelerographs. However, the seismograph was located in the El Centro Terminal Substation Building and secured to its concrete floor. Years later and after extensive research, scientists now suggest that the machine might have inaccurately recorded the strength of the earthquake due to its location. Regardless, the El Centro earthquake caused extensive and widespread damage.
The El Centro earthquake directly caused the deaths of nine people and, indirectly, seven others. Four were killed in Brawley, as a grocery store collapsed. In addition to this, over twenty persons were seriously injured. Hospitals struggled to cope with the influx of injured people who came in over the course of the next few days. The earthquake caused an estimated $6 million in direct damage, particularly to the irrigation system in the Imperial Valley. In fact, the damage to the irrigation system was so extensive, it could not be listed in detail. Fields and furrows were simply washed away by the sheer force of water that was unleashed as water towers collapsed. A huge amount of effort had to be mustered in an attempt to save the crops for that year. Canals were breached and flumes destroyed, water mains sustained multiple damages and numerous water pipes broke. The Alamo Canal, the main structure for the entire canal and irrigation system, had over seven serious breaks. In the days that followed, water rationing was imposed in Imperial Valley and Brawley. Imperial Valley itself was described as 'razed' due to the amount of damage sustained by the earthquake, with around three quarters of all buildings in Imperial Valley were heavily damaged and later condemned. In addition, windows shattered and fires broke out due to gas leaks caused by the quake. Power lines collapsed, causing widespread power outages which added to the damage and secondary effects of the earthquake. Motorists who were driving along the smooth, paved roads suddenly crashed their cars as some roads bent or had large cracks appear. Some of these cracks were impassable due to their sheer magnitude. Railroad bridges crumbled and the rails themselves were bent out of line in several places. The second shock hit the area of Brawley, damaging the town's business area as well as a quarter of homes in its residential area. Churches and temples sustained damage to their roofs and structure. Surprisingly, public schools in the area showed very little sign of damage, having been planned and constructed to be 'earthquake resistant'. The El Centro earthquake was their first test and they stood up well. Although the earthquake was named 'the El Centro earthquake', El Centro itself sustained lesser damage. In later days, multiple sand boils were spotted and there were reports of geysers in certain areas. The earthquake and aftershocks were felt as far away as Los Angeles.
Once the quake and aftershocks subsided, El Centro and surrounding areas quickly received support and aid from various sources. People came together from all backgrounds and religions to support, feed, clothe and house those who had been left with very little.
Earthquakes are still a common occurrence across the globe, so it is important to be prepared for such an event. Have a plan in place. Make sure you know the best places to go, both indoors and outdoors, in order to stay safe. It is also recommended to have a survival kit which is easily accessible. Survival kits can be purchased or you can make your own.