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Synthetics for Stress, Strain and Rotation

Description: 

The last decade has seen the increased use of DAS (distributed acoustic sensor) and rotational sensor waveforms. To facilitate the interpretation of these data, modifications are made to the wavenumber integration and modal superposition codes of Computer Programs in Seismology (Herrmann, 2013) to compute stress, strain and rotation in a cylindrical coordinate system for 1-D velocity-density models. In addition an auxiliary program is provided to rotate these to a local Cartesian system at the observation point. The complete synthetics permit an evaluation of some deductions about the joint use of rotational and translational instrumentation (6C) to estimate Rayleigh- and Love-wave phase velocities. For a plane waves propagating in the x₁ direction one can show that c_R = (du_z/dt) /ω₁₃ for an observation at the free surface and c_L = ½ (du_L/dt)/ ω₁₂ . However although c_R = (du_z/dt) /ω_rz , c_L ≠ ½ (du_L/dt)/ ω_rφ because the ω_rφ contains near both Love and Rayleigh near field terms. Love wave phase velocities can be estimated only when there is no overlapping Rayleigh wave and when wavelengths are small compared to epicentral distance.

Herrmann, R. B. (2013) Computer programs in seismology: An evolving tool for instruction and research, Seism. Res. Lettr. 84, 1081-1088, doi:10.1785/0220110096

Session: Understanding Earth Systems with Fiber-optic Cables [Poster]

Type: Poster

Date: 4/19/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Robert B. .. Herrmann

Student Presenter: No

Invited Presentation: 

Authors