The seismogram below documents a windy night at Geyser Peak station (GGP). From about 22:30 PDT on April 24 to 02:25 on April 25, the wind blew hard in coastal central California as a weather front passed through. Wind can produce low-amplitude seismic waves or "microseisms" in the earth through the action of trees, which transfer wind-generated forces into the ground through their roots. (Ocean waves also generate microseisms by the pounding of the surf.) Here, the wind-generated noise appears as an increase in the amplitude of the smallest background motions detected by this seismometer. Also, two small earthquakes are visible at 22:04 and 22:06, PDT.