Anatahan Infrasound

On April 5 th , 2005, Anatahan, a Holocene volcano in the Marianas Islands located at 16.35°N, 145.67°E, experienced the peak of its largest historical eruption, sending a column of ash 50,000 feet into the air and disrupting air traffic. The island is currently off-limits to normal traffic and its eruption cast ash and volcanic gases as far as Guam , Palau , and the Philippines . Two of three near-field seismic/acoustic monitoring stations were damaged or disabled by the ashfall. This eruption was recorded by both IS39 in Palau and IS30 in Japan (Fig. 1).

Figure 1. PMCC results from IS39. Clear signals from Anatahan volcano are present in the 0.03-.16 Hz frequency band. The x-axis is time, y-axis is frequency, and the colors represents the cross-correlation, rms amplitude, azimuth, and velocity of the coherent signals, respectively.

Using the Ground to Space (G2S) atmospheric profiles specific to the station locations and near in time to the event, source locations were estimated for the two arrivals whose times allow them to be associated with the known eruption (Fig. 2).

Figure 2. Location of Anatahan infrasonic signals recorded by IS39 and IS30.