Axial Earthquake Hypocenters
Axial Earthquake Hypocenters
Preliminary work on an automatic algorithm for locating earthquakes
Hypocenters from an automatic algorithm being developed to locate earthquakes recorded by the cabled seismic network at the summit of Axial Seamount. A triggering algorithm is used to detect earthquakes based on an increase in the ratio of RMS amplitudes in moving short- and long-term windows. Earthquake are identified based on multiple stations triggering within one second and are distinguished from whale calls based on their spectral content. A kurtosis-based picker similar to that described by Baillard et al. (2014) is used to pick P and S waves for a subset of events with the best signal to noise. Events with at least 8 picks are then located using the USGS algorithm HYPOINVERSE (Klein, 2002). The P wave model is the average of the caldera from Arnulf (2014) with the S-wave model obtained assuming VP/VS = 1.72 at depths greater than ~1 km below the seafloor and 2.5 at shallower depths. Work to optimize the picking and location procedures has not yet been completed and since these locations have not been manually verified they should be considered very preliminary.
Arnulf, A. F., Harding, A. J., Kent, G. M., Carbotte, S. M., Canales, J. P., & Nedimović, M. R. (2014). Anatomy of an active submarine volcano. Geology,42(8), 655-658.
Baillard, C., Crawford, W. C., Ballu, V., Hibert, C., & Mangeney, A. (2014). An Automatic Kurtosis‐Based P‐and S‐Phase Picker Designed for Local Seismic Networks. Bulletin of the Seismological Society of America, 104(1), 394-409.
Klein, Fred W. User's guide to HYPOINVERSE-2000: a Fortran program to solve for earthquake locations and magnitudes. US Geological Survey, 2002.