The mountains of San Gabriel are 37 miles and are long portions of the Transverse Ranges that are bordered along the northern part of the San Andreas Fault, south of the Cucamonga Fault and southwestern portion of the Serra Madre Fault. Part of the Transverse Ranges are Santa Ynez, the Santa Monica Mountains and San Bernardino. From the Islands of Channel offshore unto the Little San Bernardino Mountains which is 300 miles or 480 kilometers towards the east; that is the stretch of the domain’s ranges. At the base of San Gabriel Mountains lies its frontal fault’s system. It extends from the Fault Zone of San Jacinto located in the east to the offshore portion of Malibu located in the west. This is primarily defined by the moderate – shallow faults that are dipping northward with a vertical displacement that is estimated to be about 4,000 – 5,000 feet.
Evidences have revealed that the Transverse Ranges in the west were formed when the Pacific Plate had moved northward which was relative to the North American Plate. When the plate had shifted northwards, a part of the terrain which was parallel to the coast was rotating in a clockwise motion. This left it oriented between the east and west. The perimeter of the series of basins that have a starting point at the Santa Barbara Channel were formed by the Transverse Ranges. A few number of damaging occurrences have happened, with three situated at Santa Barbara in the years 1812, 1925, and 1978 and the other two in San Fernando Valley in the years 1971 and 1994, though other the faults in the basin that has a high Quaternary slip rate have not made any large earthquakes.
With that said, the San Fernando earthquake happened along with strong ground motion that lasted for 12 seconds. The faulting’s origin was five miles to the north of the Valley of San Fernando. Significant damage has been seen in portions localized in the valley. Not only have that but also in the foothills of the mountains of San Gabriel right above the block fault. What was responsible for the movement was the fault that had the least suspicion to cause any harm or the least threatening of all. After the event, an urgency erupted in identifying other faults that are similar to that one in the metropolitan area of Los Angeles.
Key attributes to the event considered that thrust faults within the mountains located north of Los Angeles resulted to an earthquake. This earthquake had a similar magnitude to the Northridge Earthquake in the year 1994. Both earthquakes had occurred in industrial and urban areas; both occurrences struck into the hearts of the survivors and the residents of California. The tragedies had caused Considerable economic impairment and loss of irreplaceable lives. Each of these events have prompted an urgent necessity in the careful scrutiny of the geological structure of the place, and this has been the object of study in scientific communities in the area and the planning authorities.