Southern California, 1992, Joshua Tree-Landers-Big Bear: Earthquakes following the magnitude 6.1 Joshua Tree temblor on April 22 — strong enough to rock high-rise office buildings in downtown Los Angeles more than 100 miles away — kept on migrating to the north. It began “the most substantial earthquake sequence to occur in California in the last 40 years,” according to a study published in 1993 co-written by Hauksson and Jones. The Joshua Tree quake is believed to have triggered on June 28 the magnitude 7.3 Landers earthquake in the Mojave Desert, strong enough to send shaking to Denver; a few hours later, a magnitude 6.3 hit Big Bear.

Source: Los Angeles Times June 19, 2019 09:56 UTC