At 7:18 p.m. Monday, the United States Geological Survey [USGS] recorded a magnitude 3.5 earthquake centered almost directly beneath Alida Street in Oakland.
No one has reported any injuries or significant damage, although it was the largest of a string of small but significant earthquakes around the East Bay in the past two weeks.
As of Tuesday morning, over 19,600 people reported to USGS that they felt the shaker, some as far north as Sacramento and as far south as Salinas. USGS initially reported the quake as a 3.8 but later downgraded it a few marks, as often happens.
Two weeks prior, a cluster of small earthquakes, ranging from a 2.7 to a 3.3 on the Richter Scale, similarly shook up the East Bay, although USGS recorded those quakes significantly south of Oakland, around the Danville area and closer to the related Northern Calaveras Fault, rather than the Hayward fault that runs directly beneath the town.
Since the Richter Scale increases exponentially, Monday’s 3.5 incident was nearly twice as strong as the largest 3.3 quake from the end of April, although still not particularly powerful by most Oaklander’s standards.
Geologists have warned for years that the Hayward Fault is “overdue” for a significant earthquake and that the odds favor it happening sometime in the next 30 years.
An April simulation report projected at least 800 deaths in the event of a large (7.0, about 17,700 times strong than Monday’s quake) Hayward Fault slip, and that some five percent of Oakland buildings could be destroyed or unusable in its wake.
Smaller earthquakes occasionally turn out to be what geologists call foreshocks, precursors to much larger earthquakes that follow minutes or weeks afterward. There’s essentially no way to identify a foreshock until after the larger quake comes, although the odds are that in most cases a small quake is nothing more alarming than just a small quake.
Nevertheless, all Bay Area residents should take the time to compile an earthquake kit, make an emergency plan, and get some free basic training in earthquake response, if able. Because the Big One is always just around the corner.