Regional controls on volcano seismicity along the Aleutian arc

Abstract

We identify patterns in volcano seismicity along the Aleutian arc using nearly 10 years of seismic data recorded at 46 volcanoes. The volcanoes in the central portion of the arc—those located from Aniakchak to Okmok—are associated with significantly more seismicity at depths below 15 km. We also examine the median weight percent SiO2 compositions of the seismically monitored volcanoes by compiling published geochemical data. We find that the transition between felsic volcanism in the east to more mafic volcanism in the west occurs in the same region where the depth distribution of volcanic earthquakes changes. Since deep volcanic earthquakes are often thought to be generated by the ascent of magma through the deep crust (i.e., depths > 15 km), our results suggest that magma ascent is more prolific in the central part of the arc compared to the western and eastern regions. This observation is in agreement with the location of the largest and most historically active volcanoes in the Aleutian arc, which are found in same region that generates abundant deep volcano seismicity. We propose two models to explain these apparent variations in magmatic flux: (1) a stress-based model, in which subduction obliquity and the collision of the Yakutat block affect the stress regime in the upper plate, inhibiting the rise of magma in eastern and western regions of the arc and (2) a melt-based model, where more magma is generated in the central region of the arc through increased H2O in the downgoing slab via water-laden sediments and subducting fracture zones.