Location and size of the shallowmagma reservoir beneath Kı̄lauea caldera , constraints from near - source Vp ∕ Vs ratios
نویسندگان
چکیده
We present high-resolution compressional wave to shear wave velocity ratios (Vp∕Vs) beneath Kı̄lauea’s summit caldera by applying an in situ estimation method using waveform cross-correlation data for three similar earthquake clusters. We observe high Vp∕Vs ratios (1.832 and 1.852) for two event clusters surrounded by the low background Vp∕Vs value of 1.412 at ∼2.1 km depth below the surface. These high and low Vp∕Vs ratios can be explained by meltand CO2-filled cracks, respectively, based on a theoretical crack model. The event cluster with the highest Vp∕Vs ratio consists of long-period events that followed the 1997 East Rift Zone eruption, indicating their association with fluid and magma movement. The depths of the two clusters with high Vp∕Vs ratios are consistent with the magma reservoir location inferred from geodetic observations. Their locations east and north of Halema‘uma‘u crater suggest a horizontal extent of a few kilometers for the reservoir.
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