Xiaodong Song | Geology Reports

USGS2024

Reply to “comment on ‘an evaluation of the timing accuracy of global and regional seismic stations and networks’ by Yang et al. (2021)” by Xin Zhang and Lianxing Wen

The finding of Yang et al. (2021 ; hereafter, YSR21) casts fundamental doubts on all the previous studies on the temporal changes of the inner core (IC) surface that are based on absolute arrival times, including Wen (2006 ; hereafter, WEN06) and its follow‐up studies. The reports of small time shifts of the IC‐reflected phase ( PKiKP ) likely misinterpreted station‐related issues (clock errors and instrument changes) as evidence for rapid localized deformation at the IC surface. The comment by Zhang and Wen (2024 ; hereafter, ZW24) aims at defending the results and conclusions of WEN06 by questioning a tiny portion of the results (2 out of over 400 doublets and 3 out of over 400 problematic stations) in YSR21. In response, we acknowledge an accidental error in table S1 of YSR21, which is corrected in an erratum ( Yang et al. , 2023 ), although this does not affect the results or interpretations of YSR21. However, we strongly disagree with the criticisms in ZW24 due to many problems therein, especially the issue of irreproducibility due to its inconsistent procedures with YSR21. While the problems are related to the use of absolute arrivals in the previous studies by Wen’s group, key problems in this new comment are related to questionable data selection and inconsistent processing. We further caution the metadata updates, particularly when involving small temporal change signals. We focus on the main points in ZW24 and demonstrate that its arguments are problematic in many aspects and do not diminish the credibility of YSR21 or other related works by Yang and Song in support of the IC differential rotation.

Seismological Research Letters↗

USGS2021

An evaluation of the timing accuracy of global and regional seismic stations and networks

Clock accuracy is a basic parameter of any seismic station and has become increasingly important for seismology as the community seeks to refine structures and dynamic processes of the Earth. In this study, we measure the arrival time differences of moderate repeating earthquakes with magnitude 5.0–5.9 in the time range of 1991–2017 at the same seismic stations by cross‐correlating their highly similar waveforms and thereby identify potential timing errors from the outliers of the measurements. The method has very high precision of about 10 ms and shows great potential to be used for routine inspection of the timing accuracy of historical and future digital seismic data. Here, we report 5131 probable cases of timing errors from 451 global and regional stations available from the Incorporated Research Institutions for Seismology Data Management Center, ranging from several tens of milliseconds to over 10 s. Clock accuracy seems to be a prevailing problem in permanent stations with long‐running histories. Although most of the timing errors have already been tagged with low timing quality, there are quite a few exceptions, which call for greater attention from network operators and the seismological community. In addition, seismic studies, especially those on temporal changes of the Earth’s media from absolute arrival times, should be careful to avoid misinterpreting timing errors as temporal changes, which is indeed a problem in some previous studies of the Earth’s inner core boundary.

Seismological Research Letters↗