Environmental News Network - California Quake Faults Are Highly Sensitive to Solid Earth Tides, Say Scientists

Details: By Columbia Climate School; 11.May

Rising and falling ocean tides, driven by the Earth’s daily interactions with the Moon and Sun, are familiar to almost everyone.

Cheryl Porter

Rising and falling ocean tides, driven by the Earth’s daily interactions with the Moon and Sun, are familiar to almost everyone. What many people do not realize is that the land also experiences tides, driven by the same gravitational forces. Land is more rigid than water, and so rises and falls less, but it does move, by up to 20 centimeters in some places. This is called a solid earth tide, and it produces stresses—including within earthquake faults. Is this enough to affect those faults? In some cases, the answer is yes, say scientists.

Reporting at the annual meeting of the Seismological Society of America in April, researchers said that faults in the Ridgecrest area of southwestern California trembled slightly as tidal stresses reached their cyclical maximums in the year and a half before a July 2019 sequence of sizable earthquakes.

“The signal of tidal modulation becomes extremely strong” after 2018, said Eric Beauce, a postdoctoral researcher at Columbia Climate School’s Lamont-Doherty Earth Observatory, who helped lead the research.

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California Quake Faults Are Highly Sensitive to Solid Earth Tides, Say Scientists