Aseismic inflation of Westdahl volcano, Alaska, revealed by satellite radar interferometry

Westdahl volcano, located at the west end of Unimak Island in the central A leutian volcanic are, Alaska, is a broad shield that produced moderate-size d eruptions in 1964, 1978-79, and 1991-92. Satellite radar interferometry d etected about 17 cm of volcano-wide inflation from September 1993 to Octobe r 1998. Multiple independent interferograms reveal that the deformation rat e has not been steady; more inflation occurred from 1993 to 1995 than from 1995 to 1998. Numerical modeling indicates that a source located about 9 km beneath the center of the volcano inflated by about 0.05 km(3) from 1993 t o 1998. On the basis of the timing and volume of recent eruptions at Westda hl and the fact that it has been inflating for more than 5 years, the next eruption can be expected within the next several years.