The electric field amplitude of very low frequency (VLF) transmitter from Hawaii (NPM) has been continuously recorded at Chofu (CHF), Tokyo, Japan. The VLF amplitude variability indicates lower ionospheric perturbation in the D region (60–90 km altitude range) around the NPM‐CHF propagation path. We carried out the prediction of daily nighttime mean VLF amplitude by using Nonlinear Autoregressive with Exogenous Input Neural Network (NARX NN). The NARX NN model, which was built based on the daily input variables of various physical parameters such as stratospheric temperature, total column ozone, cosmic rays, Dst, and Kp indices possess good accuracy during the model building. The fitted model was constructed within the training period from 1 January 2011 to 4 February 2013 by using three algorithms, namely, Bayesian Neural Network (BRANN), Levenberg Marquardt Neural Network (LMANN), and Scaled Conjugate Gradient (SCG). The LMANN has the largest Pearson correlation coefficient (r) of 0.94 and smallest root‐mean‐square error (RMSE) of 1.19 dB. The constructed models by using LMANN were applied to predict the VLF amplitude from 5 February 2013 to 31 December 2013. As a result the one step (1 day) ahead predicted nighttime VLF amplitude has the r of 0.93 and RMSE of 2.25 dB. We conclude that the model built according to the proposed methodology provides good predictions of the electric field amplitude of VLF waves for NPM‐CHF (midlatitude) propagation path.

The modeling and numerical analysis of seismo-electromagnetics perturbation are approached using finite-difference time-domain (FDTD) method. The research related seismo-electromagnetics perturbation recently has been implemented for earthquakes (EQs) precursor analysis by utilizing very low frequency (VLF) wave propagation. Here, the proposed method in two-dimensional (2D) form is applied to compute electromagnetics fields of the observed VLF wave and to investigate the phenomena of seismo-electromagnetics perturbation by modeling the geographical maps in two dimensions. To truncate the region of computation, the boundary condition of split-field perfectly matched layer (PML) is implemented. The parameters of investigation including the change of amplitude, frequency and time-shifting in the VLF wave are interpreted in term of changing the ionosphere layer which is confirmed as seismo-electromagnetics perturbation. From numerical result, it shows that the approaching technique using FDTD method is successfully to model the correlation between VLF wave propagation and perturbation wave associated with earthquake for different location. Moreover, some results related to time-shifting of VLF wave and frequency-influence of perturbation wave are also presented.

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Dalam kurun waktu 5 tahun terakhir, intensitas bencana alam banjir semakin sering terjadi di Kota Bengkulu. Intensitas bencana alam banjir yang demikian sering terjadi ini menjadi perhatian serius, khususnya dalam upaya pengu­rangan bahaya banjir. Salah satu area yang kerap mengalami banjir adalah Residence 2, Kelurahan Sidomulyo, Kecamatan Gading Cempaka, Kota Bengkulu, yang berada di tepi Sungai dan Bendung Air Napal. Pengabdian ini dilakukan sebagai upaya pengurangan banjir pada wilayah tersebut, dengan menerapkan teknologi maju sistem peringatan dini. Pengabdian kepada masyarakat diawali dengan menampung aspirasi dari masyarakat yang kerap mengalami banjir di saat terjadi hujan dengan intensitas sedang sampai tinggi. Selanjutnya perakitan alat pendeteksi banjir dilakukan dan diujikan. Pemasangan alat sistem peringatan dini banjir selanjutnya dilakukan dan terlebih dahulu diawali dengan sosialisasi manfaat dan cara merawat alat. Langkah berikutnya adalah dengan mengenalkan aplikasi alat ini kepada khalayak luas. Dari pengabdian ini dihasilkan bahwa respon masya­rakat terhadap keberadaan alat ini sangat baik. Masyarakat berkomitmen untuk merawat alat ini dengan baik.  Pada lokasi pengabdian, dipasanglah 2 alat sistem peringatan dini, berupa 1 transmitter dan 1 receiver. Kedua alat disebut dikembangkan dengan konsep telekomunikasi long range atau (LoRa). Kedua alat tersebut sangat handal sebagai satu kesatuan sistem peringatan dini, yang mana pada saat terjadi hujan dapat beroperasi dengan sangat efektif. Alat yang dihasilkan dan diterapkan ini dapat menjadi tonggak awal dalam upaya pengembangan sistem peringatan dini bencana di Bengkulu pada khususnya dan di Indonesia pada umumnya.

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