A series of quakes shook the mountain Friday evening and continued throughout the weekend. The first in the series, a magnitude 4.9 east-southeast of Anza at 10.6 km depth, occurred at 6:53 p.m.
That first quake was followed by four more: 3.6 magnitude at 6:54 p.m., a 2.9 and 3.0 magnitude quakes at 6:55 p.m. and a 2.6 magnitude at 6:56 p.m.
Additional quakes occurred within an hour of each other on Sunday afternoon, a 2.7 magnitude and 2.6 magnitude.
Dr. Lucy Jones (The Earthquake Lady) tweeted out “Tonight’s (Friday 4/3) M4.9 quake SE of Anza is near (maybe on) the San Jacinto Fault. The San Jacinto near Anza has had many M~5 quakes over the last few decades.”
When it comes to aftershocks, Jones tweeted: “Typical aftershocks cover a wide range. The time decay and the relative number of large to small quakes are pretty standard. But the overall productivity can vary by a thousand times. The Anza aftershocks are very normal — but on the high side of average.”
There was some concern raised by her Twitter followers if we should be nervous with the quake being less than 100 miles of the San Andreas Fault.
Jones responded: “Do not worry about the San Andreas. A M4.9 can only affect an area a few miles across. But the San Jacinto Fault itself is capable of a major equal or greater than a magnitude 7 quakes and the chance of a quake on the San Jacinto is now increased. The chance of a quake of equal or greater than a magnitude 6 is less than 1%.”