Evaluation of accelerograph data quality system based on spectrum analysis on seismic networks in Indonesia

The Meteorology, Climatology and Geophysics Agency (BMKG) since 2006 until now has installed a lot of accelerograph equipment as many as 669 station locations, to determine the quality and characteristics of the seismic noise, in this study an evaluation of the accelerograph data was carried out. The evaluation report is carried out on weekly data so that in this study, seismic noise recording data was used for 7 days from September 27 to October 3, 2021. Evaluation such as analyzing the noise level using the Probabilistic Power Spectral Density (PPSD) method. The PPSD method describes the quality of the accelerograph data compared with the signal spectral of Power Spectral Density (PSD) for 7 days with the standard accelerometer noise model, namely the Accelerometer Low-Noise Model (ALNM) and the Accelerometer High-Noise Model (AHNM) subjectively. The results of data quality analysis were evaluated by weighting the results of the PPSD analysis by 50% with other parameters by 50% in the form of Root Mean Square (RMS), amplitude ratio, percentage of data availability, number of gaps, and amount of overlap. Furthermore, based on the results of PSD signal analysis and accelerograph data, 193 locations with high cultural noise were found, 27 locations had the digitizer or sensor damages, 12 locations experienced dataless equipment response errors, and 37 locations frequently experienced data gaps. Based on the results of spectrum analysis and supporting parameters, the evaluation form of accelerograph data quality are grouped into good condition, fair condition, bad, and off condition. As a result, 669 accelerograph locations, 217 locations were good condition, 177 fair conditions, 96 bad conditions, and 179 were off condition. Finally, recommendations for locations that have fair condition and bad condition were maintenance, sensor replacement. Meanwhile, it has been suggested that location changes can be adopted if the environmental noise has extremely high.