ahmanson ranch, earthquakes, nature, trails, upper las virgenes canyon open space preserve

Were Changes in a Pool on Upper Las Virgenes Creek a Precursor to the September 2024 Malibu Earthquake?

first published & last updated
Click on thumbnails for more info & larger image.
Much-diminished pool on Las Virgenes Creek on September 11, 2024, the day before the 4.7 Malibu earthquake.
Much-diminished pool on Las Virgenes Creek on September 11, 2024, the day before the 4.7 Malibu earthquake.

It was very odd. After persisting in Upper Las Virgenes Canyon for 18 months, the pool on Las Virgenes Creek had unexpectedly receded.

When I’d run past the pool on September 6, it had been full. Just five days later — the day before the 4.7 Malibu earthquake — it had shrunk to a small puddle.

Anyone that hikes, runs, or rides in Upper Las Virgenes Canyon would be familiar with the pool — it’s where the fire road crosses the creek, about a quarter-mile south (downstream) of the pipeline monitoring station and 0.7 mile from the Las Virgenes Trailhead. A use trail has evolved to the east of the road to bypass the pool.

Pool on Las Virgenes Creek on September 17, 2024, five days after 4.7 Malibu earthquake.
Pool on Las Virgenes Creek five days after 4.7 Malibu earthquake.

The earthquake occurred on September 12, 2024, at 07:28:21 PDT. That afternoon I ran out to Upper Las Virgenes Canyon and checked the pool again. It was already refilling. Five days later it was nearly back to its normal level.

Was the change in the pool level a precursor to the Malibu earthquake?

The pool is about 11 miles from the earthquake’s epicenter. Water level changes in wells miles from an event have preceded earthquakes similar in size to the Malibu quake. It’s something to wonder about.