The orientation accuracy of three component station seismometers is very important for modern seismology research.Modern seismic studies rely heavily on precise three-component broadband observations.Similar to time travel,three dimensional particle motion is a key factor provided by a seismogram.It forms the basis of many functions,such as shear-wave splitting,re-ceiver function,and surface and normal mode studies.Three component records are often rotated to isolate longitudinal,radial,and transverse motions.A critical parameter for performing rota-tion is the geographical orientation of the two horizontal components (BHN and BHE).Because the orthogonality between components of modern broadband instruments is accurate to a fraction of a degree,what really affects a correct rotation is the orientation of the BHN component,which could deviate from the true north direction.Knowledge of the orientations of the two horizontal components is thus important to perform a correction rotation.The particle motions of teleseis-mic P waves recorded by the network were analyzed and used to estimate the north component az-imuth of each station.An SNR-weighted-multievent method was introduced to obtain component azimuths that best explain the P-wave particle motions of all the events recorded at a station.This method provides robust estimates including a measurement error calculated from background noise levels.In this study,the component azimuths of the seismic stations in Gansu province were rechecked using the P-wave particle motions of 549 MS> 6 teleseismic events from August 2007 to September 2013.Robust estimates were provided including a measurement error calculat-ed for each station in the time series.The azimuths calculated in this study are very consistent with the results of Niu (2011),which implies that the stations of Gansu province have some problems with misorientation.The SNR-weighted-multievent method can be used to effectively check the seismometer stations horizontal azimuth deviations.Therefore,we provide deviation value of the azimuth including a measurement error calculated for each station in the time series to be taken into account for any rotation based seismic studies.%利用2007年8月—2013年9月甘肃省测震台网记录的549个MS≥6远震事件的P波资料,对所属44个地震台站分量方位等问题进行检核计算.考虑到地震计维修、更换等因素,提供了甘肃省测震台网地震台站按时间序列计算的方位角偏差及方位校正变化情况,以保障测震台网数据的连续性与可靠性.研究结果表明,反演的方位偏差与文献[1]的结果基本一致,表明中国"十五"数字地震网络确实存在部分台站方位偏差较大等方面问题.因此,在进行现代地震学研究中应充分考虑台站地震计方位误差较大和研究时间段内方位角变动等因素的影响.
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