Anamolous modulations of electromagnetic field during increased seismic activity

The article presents the results of electromagnetic monitoring and geomagnetic observation during increased seismic activity in eastern part of Bishkek geodynamic range (Northern Tien-Shan) in 2017. It includes brief description of seismic conditions of the territory being researched, as well as analyses of the correlation between changes in geophysical field parameters and the earthquakes.

Investigation of Regional Geomagnetic Field Modelling in Indonesia

<p>This thesis deals with the application of the Spherical Cap Harmonic Analysis (SCHA) modelling technique to obtain geomagnetic field models for Indonesia, which have better resolution and accuracy than the International Geomagnetic Reference Field (IGRF). B-splines basis function and autoregressive forecasting are applied to improve estimates of secular variation and its forecast over the Indonesian region. The modelling technique is applied to geomagnetic observation data compiled from 68 geomagnetic repeat stations in Indonesia covering the period 1985 - 2015 from BMKG (Badan Meteorologi Klimatologi dan Geofisika / Agency for Meteorology, Climatology, and Geophysics) Indonesia, definitive data from five BMKG geomagnetic observatories and 13 INTERMAGNET (The International Real-Time Magnetic Observatory Network) observatories. Synthetic cartesian X, Y, and Z components at sea level at 17 fixed locations, calculated from IGRF-13, are also used. The area covered by the models in this thesis is the Indonesian region with a spherical cap half-angle of 30° and with the coordinate of the spherical cap pole at 122°E and 3°S. From statistical analysis and comparison with the IGRF, the SCHA model with index k = 7 is considered as the best SCHA model, both in resolution and accuracy. Compared with the root mean square deviation (RMSD) of the IGRF model, the RMSD of the SCHA model with index k = 7 is lower by 28 nT, 11 nT, and 34 nT for X, Y, and Z components, respectively. A model from interpolation of the SCHA with index k = 7 using the B-splines basis function for the year 1985.5 – 2015.5 shows that the SCHA model gives better results than the IGRF. The forecasting calculation for the year 2015.5 – 2020.5 suggests that the autoregressive order 3 of the SCHA with index k = 7 gives better results than the forecasting of the IGRF model, especially in the X, Z, and F components. However, in the Y component, the IGRF is still better than the SCHA model. The RMSD of the forecasted SCHA model is 154.92 nT, 200.87 nT, 104.39 nT, and 135.81 nT for X, Y, Z, and F components, respectively, while the RMSD of the IGRF model is 172.62 nT, 95.52 nT, 117.55 nT, and 162.38 nT for X, Y, Z, and F components. Thus, the forecasted SCHA model is suitable for data reduction of geomagnetic surveys in the Indonesian region but not preferable for navigation.</p>

Investigation of Regional Geomagnetic Field Modelling in Indonesia

<p>This thesis deals with the application of the Spherical Cap Harmonic Analysis (SCHA) modelling technique to obtain geomagnetic field models for Indonesia, which have better resolution and accuracy than the International Geomagnetic Reference Field (IGRF). B-splines basis function and autoregressive forecasting are applied to improve estimates of secular variation and its forecast over the Indonesian region. The modelling technique is applied to geomagnetic observation data compiled from 68 geomagnetic repeat stations in Indonesia covering the period 1985 - 2015 from BMKG (Badan Meteorologi Klimatologi dan Geofisika / Agency for Meteorology, Climatology, and Geophysics) Indonesia, definitive data from five BMKG geomagnetic observatories and 13 INTERMAGNET (The International Real-Time Magnetic Observatory Network) observatories. Synthetic cartesian X, Y, and Z components at sea level at 17 fixed locations, calculated from IGRF-13, are also used. The area covered by the models in this thesis is the Indonesian region with a spherical cap half-angle of 30° and with the coordinate of the spherical cap pole at 122°E and 3°S. From statistical analysis and comparison with the IGRF, the SCHA model with index k = 7 is considered as the best SCHA model, both in resolution and accuracy. Compared with the root mean square deviation (RMSD) of the IGRF model, the RMSD of the SCHA model with index k = 7 is lower by 28 nT, 11 nT, and 34 nT for X, Y, and Z components, respectively. A model from interpolation of the SCHA with index k = 7 using the B-splines basis function for the year 1985.5 – 2015.5 shows that the SCHA model gives better results than the IGRF. The forecasting calculation for the year 2015.5 – 2020.5 suggests that the autoregressive order 3 of the SCHA with index k = 7 gives better results than the forecasting of the IGRF model, especially in the X, Z, and F components. However, in the Y component, the IGRF is still better than the SCHA model. The RMSD of the forecasted SCHA model is 154.92 nT, 200.87 nT, 104.39 nT, and 135.81 nT for X, Y, Z, and F components, respectively, while the RMSD of the IGRF model is 172.62 nT, 95.52 nT, 117.55 nT, and 162.38 nT for X, Y, Z, and F components. Thus, the forecasted SCHA model is suitable for data reduction of geomagnetic surveys in the Indonesian region but not preferable for navigation.</p>

Analisis Pola Waktu Mula Anomali Polarisasi Sinyal Sebelum Gempa Bumi Di Wilayah Aceh Dan Sumatera Utara

Telah dilakukan penelitian mengenai pola waktu mula anomali polarisasi sinyal geomagnet yang dapat dijadikan sebagai parameter dalam menentukan tanda atau gejala sebelum gempa bumi dengan menggunakan data komponen magnetik yang diperoleh dari pengamatan geomagnetik di Obsevatorim Badan Meteorologi Klimatologi Geofisika Tungtungan. Penelitian ini bertujuan untuk mengetahui pola waktu mula anomali polarisasi sebelum gempa bumi di wilayah Aceh dan Sumatera Utara terjadi. Gempa bumi yang di invertigasi merupakan gempa bumi yang terjadi di Sumatera Utara dan Aceh pada periode 2012-2015 dan memiliki magnitude > 5 SR. Polariasi dilakukan dengan membandingkan data geomagnet komponen H dan Z. Transformasi fourier diperlukan untuk merubah sinyal menjadi domain frekuensi. Kemudian dilakukan penapisan frekuensi sinyal pada spektrum 0,05-0,02 Hz. Spektrum ini dipilih karena berkaitan dengan aktivitas sebelum gempa. Hasil polarisasi sinyal dibandingkan dengan data Indeks Dst untuk menentukan waktu mula anomali yang berasal dari aktivitas gempa. Selanjutnya dilakukan analisis pola waktu tehadap magnitudo gempa. Berdasarkan pola yang telah dihasilkan menggambarkan bahwa pola waktu mula anomali yang semakin lama akan menghaslkan magnitudo gempa yang lebih besar. Kata kunci: Anomali Polarisasi, Sinyal Geomagnet, Gempa Bumi, Indeks Dst Research on the time pattern of anomaly polarization of geomagnetic signals can be used as a parameter in determining the signs or symptons before the earthquake using magnetic component data obtained from geomagnetic observation in Observatorium Meteorology Climatology Geophysics Tungtungan. The purpose of this reseach is to know the time pattern of polarization anomaly before earthquake in Aceh and North Sumatera region. The investigated earthquake is an earthquake in the period 2012-2015. Polarization is done by comparing geomagnetic data of H and Z components. Fourier transform are needed to convert signals into frequency domains. Then performed signal frequency filtering on spectrum 0,05-0,02 Hz. this spectrum was chosen because it is related to activity before the earthquake. The result of the signal polarization is compared with the Dst Index data to determine the starting time of the anomaly derivedfrom the earthquake activity. Furthermore, the time pattern analysis was made to the anomaly starting time pattern that will prolog the magnitude of the larger earthquake. Keywords : Polarization Anomaly, Geomagnet Signal, Earthquake, Index Dst