With much of Southern California still recovering from wildfires, the northern part of the state has received a stark reminder of a different kind of environmental threat—earthquakes.

The largest earthquake to hit the San Francisco Bay area in nearly two decades struck last Tuesday with a magnitude of 5.6. This tremor, centered near San Jose, lasted half a minute and was felt as far away as Oregon.

No one was reported killed or hurt from the quake, but geological experts warn that it is a sign of much worse to come.

Tuesday’s quake “significantly increased the probability” of a detrimental earthquake coming from one or both of two nearby fault lines according to the California Earthquake Prediction Evaluation Council, a board that advises the state’s Office of Emergency Services on quake forecasts. Those faults are capable of producing a 7.0 magnitude earthquake or even higher, reports the Salinas Californian.

California lies on the Pacific Rim “Ring of Fire,” a seismically active area lined by volcanoes and fault lines, which circles around the Pacific Ocean all the way to China.

The Asian side of the Pacific Rim has experienced some worrying geological activity. In mid-October, the Indonesian government warned of impending volcanic eruptions from Mount Kelud and ordered 30,000 people living on its slopes to evacuate.

The Philippines, the Marianas Islands, and Sumatra, Indonesia, have all experienced powerful earthquakes recently.

Nations all around the Pacific Rim constantly monitor for earthquakes, volcanoes and tsunamis, but these governments can neither prevent nor reduce the magnitude of any earthquake that strikes. The best governments and residents can do is prepare, though in California, where scientists say the “Big One” is long overdue, even that is being put off. Only 12 percent of homeowners hold expensive earthquake insurance, and most are ill-prepared for such an environmental disaster.

To learn more about why natural disasters occur and whether they can, in fact, be prevented, read “Did the Tsunami Shake Your Faith?”