Transdimensional surface wave tomography: a one-step approach

Ambient-noise surface wave tomography has proven to be an effective tool for ۳D crustal imaging. Conventionally, a two-step inversion approach is adopted. That is, a first inversion results in separate, frequency-dependent ۲D surface-wave velocity maps, upon which local frequency-to-depth inversions are performed. As such, a ۳D seismic velocity distribution is recovered effectively. In our case, phase velocities are used. A one-step ۳D non-linear algorithm has recently been proposed in a Bayesian framework using reversible jump Markov chain Monte Carlo called transdimensional tomography. This approach has several advantages over the two-step approach, with the most notable being the fact that the one-step approach preserves spatial correlation information in ۳D. In this study, we image the shear wave velocity structure of the Reykjanes Peninsula using the recently developed one-step ۳D transdimensional surface wave tomography. The transdimensional tomography algorithm uses a variable model parametrization by employing Voronoi cells in conjunction with the reversible jump Markov chain Monte Carlo method. We use the frequency dependent-travel times (with a frequency range of ۰.۱-۰.۵ Hz) derived from the recorded ambient noise data to image the area. The results show that the algorithm successfully recovered the velocity structure below the areas sampled with sufficient ray path coverage. The areas with fewer ray paths result in a smoother velocity structure. We observe a few low-velocity anomalies at depths around ۴-۶ km, likely associated with the high-temperature fields around those depths.

کلیدواژه ها:

Transdimensional tomography ، surface wave dispersion ، surface wave inversion ، Markov chain Monte Carlo ، seismic tomography