Transdimensional surface wave tomography: a one-step approach
عنوان دوره: بیستمین کنفرانس ژئوفیزیک ایران
نویسندگان
1Department of Geoscience and Engineering, Delft University of Technology, 2628 CN Delft, The Netherlands
2Department of Geoscience and Engineering, Delft University of Technology, The Nederlands
3University of Edinburgh
چکیده
Ambient-noise surface wave tomography has proven to be an effective tool for 3D crustal imaging. Conventionally, a two-step inversion approach is adopted. That is, a first inversion results in separate, frequency-dependent 2D surface-wave velocity maps, upon which local frequency-to-depth inversions are performed. As such, a 3D seismic velocity distribution is recovered effectively. In our case, phase velocities are used. A one-step 3D 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 3D. In this study, we image the shear wave velocity structure of the Reykjanes Peninsula using the recently developed one-step 3D 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 0.1-0.5 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 4-6 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
Title
Transdimensional surface wave tomography: a one-step approach
Authors
Amin Rahimi Dalkhani, Cornelis Weemstra, Xin Zhang
Abstract
Ambient-noise surface wave tomography has proven to be an effective tool for 3D crustal imaging. Conventionally, a two-step inversion approach is adopted. That is, a first inversion results in separate, frequency-dependent 2D surface-wave velocity maps, upon which local frequency-to-depth inversions are performed. As such, a 3D seismic velocity distribution is recovered effectively. In our case, phase velocities are used. A one-step 3D 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 3D. In this study, we image the shear wave velocity structure of the Reykjanes Peninsula using the recently developed one-step 3D 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 0.1-0.5 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 4-6 km, likely associated with the high-temperature fields around those depths.
Keywords
Transdimensional tomography, surface wave dispersion, surface wave inversion, Markov chain Monte Carlo, seismic tomography