TY - JOUR
T1 - On waveform correlation measurement uncertainty with implications for temporal changes in inner core seismic waves
AU - Lythgoe, Karen H.
AU - Inggrid, Maria I.
AU - Yao, Jiayuan
N1 - Funding Information:
We use Taup ( Crotwell et al. 1999 ) and GMT ( Wessel et al. 2013 ). The cc_sac code is freely available at https://github.com/core-man/repeating-earthquake and uses the FFTW subroutine library ( www.fftw.org ). We thank Dr. Lupei Zhu who wrote the sac_wfcc code and Dr. Zhigang Peng who makes the code available for downloaded at http://geophysics.eas.gatech.edu/people/zpeng/Teaching/SAC_Tutorial . Matlab xcorrFD (cross-correlation in frequency domain) is obtained from MATLAB central file exchange (retrieved 4th August 2020). We thank the editor Vernon Cormier and two anonymous reviewers for constructive feedback that improved the article. We thank Michael Braim for the original inspiration to undertake this work. This is Earth Observatory of Singapore contribution number 334. This work is supported by a Nanyang Presidential Postdoctoral Fellowship awarded to K.L. (No. 04INS000845A620 ). CRediT author statement - K.L.: Conceptualisation, Investigation, Supervision, Writing; M.I. Investigation, Visualisation, Writing; J.Y.: Data curation, Software, Writing.
Funding Information:
We use Taup (Crotwell et al. 1999) and GMT (Wessel et al. 2013). The cc_sac code is freely available at https://github.com/core-man/repeating-earthquake and uses the FFTW subroutine library (www.fftw.org). We thank Dr. Lupei Zhu who wrote the sac_wfcc code and Dr. Zhigang Peng who makes the code available for downloaded at http://geophysics.eas.gatech.edu/people/zpeng/Teaching/SAC_Tutorial. Matlab xcorrFD (cross-correlation in frequency domain) is obtained from MATLAB central file exchange (retrieved 4th August 2020). We thank the editor Vernon Cormier and two anonymous reviewers for constructive feedback that improved the article. We thank Michael Braim for the original inspiration to undertake this work. This is Earth Observatory of Singapore contribution number 334. This work is supported by a Nanyang Presidential Postdoctoral Fellowship awarded to K.L. (No. 04INS000845A620). CRediT author statement - K.L.: Conceptualisation, Investigation, Supervision, Writing; M.I. Investigation, Visualisation, Writing; J.Y.: Data curation, Software, Writing.
Publisher Copyright:
© 2020 The Authors
PY - 2020/12
Y1 - 2020/12
N2 - We address the uncertainty related to cross-correlation waveform time shift measurements, particularly related to temporal changes in inner core seismic waves. Details of the cross-correlation measurement, including data processing, window length, pick time, sampling rate and the algorithm itself, all affect the calculated time shift. By systematically varying measurement parameters for a set of earthquake doublets we find time shift uncertainties of 0.01 s and 0.02 s for differential times and double differential times respectively. The uncertainty is of a similar magnitude to reported double differential times of PKIKP and PKiKP inner core phases. Accounting for measurement uncertainty results in 80% of values published in a recent study being below the measurement resolution (Yang and Song 2020a). While the temporal variations in inner core phases is not in dispute, properly accounting for uncertainties is needed for robust data interpretation. A re-assessment for the origin of inner core temporal changes is therefore warranted and future studies should account for measurement uncertainty.
AB - We address the uncertainty related to cross-correlation waveform time shift measurements, particularly related to temporal changes in inner core seismic waves. Details of the cross-correlation measurement, including data processing, window length, pick time, sampling rate and the algorithm itself, all affect the calculated time shift. By systematically varying measurement parameters for a set of earthquake doublets we find time shift uncertainties of 0.01 s and 0.02 s for differential times and double differential times respectively. The uncertainty is of a similar magnitude to reported double differential times of PKIKP and PKiKP inner core phases. Accounting for measurement uncertainty results in 80% of values published in a recent study being below the measurement resolution (Yang and Song 2020a). While the temporal variations in inner core phases is not in dispute, properly accounting for uncertainties is needed for robust data interpretation. A re-assessment for the origin of inner core temporal changes is therefore warranted and future studies should account for measurement uncertainty.
KW - Inner core differential rotation
KW - Temporal change of inner core waves
KW - Waveform cross-correlation
UR - http://www.scopus.com/inward/record.url?scp=85096461165&partnerID=8YFLogxK
U2 - 10.1016/j.pepi.2020.106606
DO - 10.1016/j.pepi.2020.106606
M3 - Article
AN - SCOPUS:85096461165
SN - 0031-9201
VL - 309
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
M1 - 106606
ER -