BMKG MOMENT MAGNITUDE DETERMINATION FOR IMPROVING THE QUALITY INFORMATION PRODUCTS OF INATEWS

• Main Author: Fahmi Nugraha, Muhammad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/66798
• Institution: Institut Teknologi Bandung

The Meteorology, Climatology and Geophysics Agency (BMKG), part of the Indonesia Tsunami Early Warning System (InaTEWS), is obliged to provide earthquake information or tsunami early warnings within five minutes after the earthquake. Seismic parameters determined by BMKG (one of which is the magnitude) in the first five minutes are the result of data processing from seismic stations that are recorded during that time so that all BMKG seismic stations have not recorded the occurrence of the earthquake. This causes fluctuations in the determination of the magnitude and also causes a difference between the initial magnitude that is informed and the final magnitude after all seismic stations have recorded it. The initial magnitude value is also often different from the moment magnitude (Mw BMKG), which results from the moment tensor inversion. These parameters were obtained more than five minutes after the earthquake. This study aims to reduce fluctuations in the magnitude value in the early minutes after an earthquake by categorizing the best station in determining the magnitude, accelerating the determination of Mwp, and increasing the accuracy of determining the magnitude in the first five minutes by updating the magnitude estimation formulation Mw(mB), Mw(Mwp). and make a magnitude summary of the updated magnitude estimation formulation. The results of this study succeeded in determining the categorization of primary and secondary seismic stations. The primary category consists of 285 stations that can be used in determining the location and magnitude of an earthquake. The secondary category consists of 126 stations which are only used in determining the location of an earthquake. In addition, the determination of Mwp can be accelerated if it is determined by a seismic station with an epicentral distance starting from 1o. This study also succeeded in obtaining a new formulation for the specific magnitudes of Mw(mB) and Mw(Mwp) with a coefficient of determination R2 of 0.81 and 0.84, respectively. Next, a new magnitude summary is created, with coefficients c and constant d - 0.95 and -0.2 for the new (w) Mw(Mwp) weights and 0.4 and -0.1 for the new (w) Mw( mB) new. The test results and validation using SeisComP playback show that determining the magnitude with the primary station can reduce fluctuations in the early minutes of the magnitude calculation. Then the determination of Mwp can be accelerated + 50 seconds to 2 minutes after the earthquake. In addition, the new Mw(mB) and Mw(Mwp) show better results than the BMKG results, and the summary magnitude Mw_est_avg is the best type of magnitude that is most accurate in estimating Mw BMKG and can be used as the magnitude sent in InaTEWS seismic information.