Assessing Short-Term Clock Errors and Drifts of Temporary Seismic Networks Using the Active Airgun Source in Binchuan, Yunnan

摘要

We conducted a short-term airgun experiment at the Binchuan Fixed Airgun Signal Transmission Station from 14 to 20 February 2017, and two different types of seismometers (Guralp CMG-40T and QS05A) recorded 62 airgun shots triggered under the same conditions. However, we observed significant clock errors and drifts in seismic data recorded by four QS05A seismometers. To assess the short-term clock errors and drifts for seismometers, we propose a new method that measures the P-wave arrival-time differences between airgun signals recorded at a station pair, using the matched filter method. We find similar to 1.0 s absolute clock errors for two Guralp CMG-40T stations (CKT2 and 53261) and one QS05A station (STA05), as well as similar to 0.5 s timing leaps for four QS05A stations (STA19, STA21, STA31, and STA33) during the experiment. Furthermore, all the QS05A seismometers exhibit clock drifts with similar linear trends. Additionally, we use teleseismic waveforms to verify the absolute clock errors for stations CKT2, 53261, and STA05. After double-checking several possible factors, we determine the hardware failure or malfunctioning that may cause clock errors for the two types of seismometers.