seisflows.tools.noise

Preprocessing tools for the ambient noise adjoint tomography Noise Inversion workflow module. Tools here are used for waveform rotation required for horizontal component sensitivity kernels (RR and TT).

Functions

rotate_ne_trace_to_rt(tr_ee, tr_ne, tr_en, tr_nn, ...)

Used during ambient noise adjoint tomography (workflow: noise inversion) to

rotate_rt_adjsrc_to_ne(tr, theta, theta_p)

Rotate RR and TT adjoint sources to N and E components for use in

Module Contents

seisflows.tools.noise.rotate_ne_trace_to_rt(tr_ee, tr_ne, tr_en, tr_nn, theta, theta_p)

Used during ambient noise adjoint tomography (workflow: noise inversion) to rotate N and E component Synthetic Greens Functions (SGF) to R and T components so that they can be directly compared to RR and TT Empirical Greens Functions (EGF)

Naming convention: AB (A=force source direction, B=waveform component) Order of input follows Wang et al. 2019 Eqs. 9 and 10

Parameters:

  • tr_ee (obspy.core.trace.Trace) – E component FORCE, E component SGF

  • tr_ne (obspy.core.trace.Trace) – N component FORCE, E component SGF

  • tr_en (obspy.core.trace.Trace) – E component FORCE, N component SGF

  • tr_nn (obspy.core.trace.Trace) – N component FORCE, N component SGF

  • theta (float) – azimuth between source station and receiver station in units of radians (see Wang et al. 2018 Fig. 1)

  • theta_p (float) – theta prime, 180 degrees from the backazimuth of the source station and receiver station in units radians. theta != theta_prime for a spherical Earth, but they will be close.

seisflows.tools.noise.rotate_rt_adjsrc_to_ne(tr, theta, theta_p)

Rotate RR and TT adjoint sources to N and E components for use in N and E component adjoint simulations in ambient noise inversion workflow.

Paraphrasing Wang et al. (2019) 2.2.2

Kernels are generated from the time convolution of a forward field due to a point force in the [east or north] direction, and an adjoint field obtained by injecting [f_TT or f_RR (adjoint source)] in the east and north directions at the receiver, with their amplitude modulated by the rotation matrix.

Parameters:

  • tr (obspy.core.trace.Trace) – input trace that is either R or T component. Component stat of the Trace is required (Trace.stats.component)

  • theta (float) – azimuth between source station and receiver station in units of radians

  • theta_p (float) – theta prime, 180 degrees from the backazimuth of the source station and receiver station in units radians. theta != theta_prime for a spherical Earth, but they will be close.

Return type:

tuple of obspy.core.trace.Trace

Returns:

(EE, NE, EN, NN) component adjoint sources that have been rotated based on the component of tr_in