June 14, 2015
Carl Tape, ctape@alaska.edu
Contributions to NSF Annual report for Geoinformatics award
Community Computational Platforms for Developing Three-Dimensional Models of Earth
Structure, Phase II
T.H. Jordan (PI), P. Chen, Y. Cui, J.H. Shaw, J. Tromp
1. A summary of your research accomplishments over the past year. No more than one
page. Include impact on principal discipline.
A. Numerical resolution of seismic wavefield simulations in southern California.
Quantification of numerical resolution of seismic wavefield simulations is an important step in
the inversion framework. In Tape and Casarotti (2014 AGU) we demonstrate the wide range of
minimum resolvable periods that are present within complex crustal models such as the CVM-H
model in southern California. By knowing the minimum resolvable period for each path (source
to station) in the model, we can identify the period range over which (1) we can interpret the
synthetic seismograms from the forward simulations and (2) we can make measurements for a
tomographic inversion. A formal publication would help establish this numerical test within the
seismic inversion framework; we intend to expand the results from the AGU abstract into a paper.
Furthermore, we have teamed up with Lion Krischer to disseminate the algorithm as a pythonbased code (see 2.), which should encourage the widest adoption possible.
B. The effect of topography on the seismic wavefield.
A master’s student at UAF (Ulrika Miller, formerly Ulrika Cahayani) completed an analysis of
the effect of topography on the seismic wavefield in southern California. She used 137 previously
studied earthquakes in southern California (from Tape et al., 2009) and examined wavefield
differences from simple models (homogeneous and layered) with and without topography. Her
results revealed the largest effects in directions that were nodal to the source mechanisms. Overall
the effects of topography at the regional scale of southern California are small compared to the
effects of 3D variations in velocity structure.
C. Implementation of python-based inversion framework.
The adjoint inversions performed by Tape et al. (2009, Science) and by Zhu et al. (2012, Nature
Geoscience) relied on SPECFEM3D for calculating synthetic seismograms and event kernels, and
they relied on a combination of shell/Perl scripts, fortran codes, matlab codes, and sac libraries
for the iterative inversion. The Princeton group continues to lead an effort to improve the
inversion framework, with emphasis on the optimization routines. The modules for picking time
windows for measurements, making measurements, and making adjoint sources have been
rewritten in python and obspy. In summer 2015 we are starting to use these newly developed
modules on three different target regions: Carl Tape in southern California (this project), Vipul
Silwal in Alaska, and Amir Allam in the San Jacinto fault zone. We hope the new workflow will
promote reproducible results and also lower the threshold for others to perform adjoint-based
inversions.
D. Adjoint inversion of CVM-H.
This remains the goal for Year 2 of Phase II. The inversion will emphasize periods 4 s and longer.
2. A short statement on broader impacts you have accomplished, including dissemination of
results.
Codes that are developed for the project will be shared via open-source code repositories, such as
on github. Wavefield simulations will be shared on youtube.
Movie:
http://youtu.be/Tx-u_HULFnY
Scenario earthquake in southern California within a simple crust + mantle model that contains the
Harvard San Joaquin basin model.
Codes:
https://github.com/krischer/wfdiff
Lion Krischer wrote the algorithm of Tape and Casarotti (2014 AGU) in python and obspy. The
code is open-source but is under development.
3. A list of any papers you have published or submitted, including the journal, authors, dates,
doi numbers, etc.
None submitted. (Co-author on Shaw et al., 2015 EPSL) Two papers planned for submission
based on the 2014 AGU abstracts.
4. A list of any abstracts of talks you have given including the meeting name, location, titles,
and authors.
(Note that Ulrika Cahayani changed her name to Ulrika Miller after she got married in 2014.)
Tape, C., and E. Casarotti (2014), Numerical resolution of seismic wavefield simulations in
southern California, Abstract S42A-08 presented at 2014 Fall Meeting, AGU, San Francisco,
Calif.,
15-19 Dec.
Cahayani, U., and C. Tape (2014a), The e_ect of topography on the seismic wavefield, Abstract
presented at the 2014 SSA Annual Meeting, Anchorage, Alaska, April 30 - May 2.
Cahayani, U., and C. Tape (2014b), The e_ect of topography on the seismic wavefield, Abstract
S41E-05 presented at 2014 Fall Meeting, AGU, San Francisco, Calif., 15-19 Dec.
Miller, U. (2014), The effect of topography on the seismic wavefield, Master's thesis, U. of
Alaska
Fairbanks.
5. A list of staff, post-docs, or students you have supported with a 25-word statement on what
they are doing on the project, their status (grad student, undergrad, staff, etc.), and their email address.
Ulrika Cahayani Miller (ucahayani@alaska.edu) was supported on funds separate from the
geoinformatics project, through her research was relevant to the project. My effort to assist her in
most aspects of her research was supported by the geoinformatics project. Ulrika successfully
defended her master’s thesis in Dec 2014. She is a female student from Indonesia.
25 words: Ulrika conducted a master’s thesis (granted 2014) to quantify the effect of topography
on the seismic wavefield in southern California.
6. A list of any countries you have visited for research on this project.
None.
7. Any collaborators you might have in addition to the team here and their affiliation.
Lion Krischer, PhD student at Munich University, krischer@geophysik.uni-muenchen.de
Lion is collaborating on the study to quantify minimum resolvable periods. He rewrote our
procedures in python and obspy (see github link in 2).
8. If you have a particularly compelling figure, please send with a caption.
None provided.