The Thai Meteorological Department (TMD) seismic network began development in 2008. There are a total of 71 seismic stations consisting of 26 borehole stations and 45 surface stations currently installed. The three-component data from the TMD seismic network have been widely used in previous seismological studies. In a recent analysis, we have found that sensor orientation as reported in the site metadata is sometimes significantly incorrect, especially for borehole stations. In this study, we analyze P-wave polarization data from regional and teleseismic earthquakes recorded in the network to estimate the true instrument orientation relative to geographic north and compare that to station metadata. Of the 45 surface stations, we found that at present, ~ 82% are well oriented (i.e., aligned within 0–15° of true north). However, 8 sites have sensors misoriented by more than 15°, and some stations had a temporal change in sensor orientation during an upgrade to the seismic system with replacement of the sensor. We also evaluated sensor orientations for 26 TMD borehole seismic stations, from 2018 to the 2022. For many of the borehole stations, the actual sensor orientation differs significantly from the TMD metadata, especially at short-period stations. Many of those stations have sensor misorientations approaching 180°, due to errors in the ambient noise analysis calibration techniques used during installation. We have also investigated how this sensor misorientation affects previous seismic studies, such as regional moment tensor inversion of earthquakes sources and receiver function stacking. We have found that the large deviations in sensor orientation can result in erroneous results and/or large measurement errors. A cause of the orientation error for borehole sites could be a combination of strong background surface ambient seismic noise coupled with an incorrect reference instrument response.

中文翻译：

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根据 P 波质点运动对 TMD 地震台网（泰国）的传感器定位

泰国气象局 (TMD) 地震台网于 2008 年开始建设。目前共有 71 个地震台站，其中包括 26 个钻孔台站和 45 个地面台站。TMD地震台网的三分量数据在以往的地震研究中得到了广泛的应用。在最近的分析中，我们发现站点元数据中报告的传感器方向有时明显不正确，尤其是对于钻孔站。在这项研究中，我们分析了网络中记录的区域地震和远震地震的 P 波偏振数据，以估计相对于地理北方的真实仪器方向，并将其与台站元数据进行比较。在 45 个地面站中，我们发现目前约有 82% 的站定向良好（即在真北 0–15° 范围内对齐）。然而，8 个站点的传感器方向错误超过 15°，并且一些站点在更换传感器以升级地震系统期间传感器方向发生了时间变化。我们还评估了 26 个 TMD 钻孔地震台站的传感器方向，从 2018 年到 2022 年。对于许多钻孔台站，实际传感器方向与 TMD 元数据有很大不同，尤其是在短周期台站。由于安装过程中使用的环境噪声分析校准技术的错误，其中许多站点的传感器方向错误接近 180°。我们还研究了这种传感器的错误定位如何影响以前的地震研究，例如震源的区域矩张量反演和接收函数叠加。我们发现传感器方向的大偏差会导致错误的结果和/或大的测量误差。钻孔位置定向误差的一个原因可能是强烈的背景表面环境地震噪声与不正确的参考仪器响应相结合。