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All Journal Journal of Mathematical and Fundamental Sciences JURNAL METEOROLOGI DAN GEOFISIKA Jurnal Geofisika Jurnal Tanah dan Iklim
Nanang T. Puspito
Institut Teknologi Bandung (ITB)
Agriculture, Biological Sciences & Forestry Astronomy Chemistry Earth & Planetary Sciences Energy Mathematics Physics

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PENENTUAN NILAI AMBANG CURAH HUJAN UNTUK DETEKSI DINI KEKERINGAN PADA TANAMAN PADI SAWAH: STUDI KASUS PROVINSI JAWA BARAT DAN SULAWESI SELATAN Surmaini, Elza; Hadi, Tri Wahyu; Subagyono, Kasdi; Puspito, Nanang Tyasbudi
Jurnal Tanah dan Iklim (Indonesian Soil and Climate Journal) Vol 38, No 2 (2014)
Publisher : Balai Besar Penelitian dan Pengembangan Sumberdaya Lahan Pertanian

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21082/jti.v38n2.2014.79-87

Abstract

Abstrak. Defisit curah hujan dalam periode tertentu merupakan faktor dominan yang menentukan kekeringan agronomis. Oleh karena itu, nilai ambang curah hujan sebelum waktu tanam yang berpotensi menyebabkan kekeringan perlu diketahui untuk deteksi dini. Penelitian ini bertujuan untuk mengkonfirmasi bahwa penurunan curah hujan menyebabkan kekeringan agronomis pada tanaman padi sawah dan menentukan nilai ambang curah hujan yang berpotensi menyebabkan pada musim kemarau. Nilai ambang curah hujan dianalisis secara statistik menggunakan persamaan regresi polinomial antara Indeks Dampak Kekeringan Padi (IDKP) dengan curah hujan dan debit sungai. Model GR4J digunakan untuk menentukan korelasi antara curah hujan dan debit serta mensimulasi debit sungai pada tahun-tahun El Niño. Hasil analisis menunjukkan bahwa curah hujan cukup akurat digunakan sebagai indikator untuk deteksi dini kekeringan agronomis tanaman padi pada sawah tadah hujan dan sawah irigasi. Nilai ambang curah hujan pada sawah tadah hujan adalah 60-70 mm, sedangkan untuk sawah irigasi adalah 20 mm. Abstract. Prolonged deficit of rainfall is a dominant factor affecting drought severity. Therefore, rainfall threshold prior to planting time that potentially lead to agronomic drought need to be identified for early detection purpose. This research aimed to confirm the adequacy of rainfall for measuring drought on paddy rice, and to assess rainfall thresholds as indicator of drought on paddy rice during dry season planting. Rainfall thresholds were statistically analyzed using a polynomial regression between Paddy Drought Impact Index (PDII) and rainfall and river discharge. GR4J model was used to assess correlation between rainfall and river discharge and to simulate river discharge in El Niño years. We deduce that rainfall is an appropriate indicator for early detection agronomic drought for both rainfed and irrigated paddy rice. We also emphasize that the drought events should be predicted by rainfall thresholds whose values are 20 mm for irrigated paddy field and between 60 mm to 70 mm in rainfed paddy field.
Characteristics of Earthquake-Generated Tsunamis in Indonesia Based on Source Parameter Analysis Sugeng Pribadi; A. Afnimar; Nanang T. Puspito; Gunawan Ibrahim
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 2 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.2.8

Abstract

We have characterized 27 earthquake-generated tsunamis from 1991 to 2012 in Indonesia, based on source parameter analysis. This includes the focal mechanism derived by W phase inversion analysis, the ratio (Θ) between the seismic energy (E) and the seismic moment (Mo), the moment magnitude (Mw), the rupture duration (To) and the distance of the hypocenter to the trench. Most of the earthquakes (24 events) were tsunamigenic earthquakes with various fault types, a shallow focal depth (12 km ≤ D ≤ 77.8 km), a small to large magnitude (6.6 ≤ Mw ≤ 9.0), a low ratio of seismic energy to seismic moment (-5.8 < Θ < -4.9), a short to long rupture duration (27 s ≤ To ≤ 257 s), a small to large tsunami height (0.1 m ≤ H ≤ 50.9 m) and a short to long distance from the hypocenter to the trench (10 km < HT ≤ 230 km). Three tsunami earthquakes were characterized by a thrust fault mechanism, a very shallow depth (D ≤ 20 km), a moderate magnitude (7.5 ≤ Mw ≤ 7.8), a very low ratio of seismic energy to seismic moment (Θ ≤ -5.8), a long rupture duration (99 s ≤ To ≤ 135 s), a large tsunami height (7.4 m ≤ H ≤ 14 m) and a short distance from the hypocenter to the trench (HT ≤ 20 km).
ANALISIS VARIASI GPS – TEC YANG BERHUBUNGAN DENGAN GEMPABUMI BESAR DI SUMATERA Hendri Subakti; Nanang T. Puspito; Djedi S. Widarto
Jurnal Meteorologi dan Geofisika Vol 9, No 1 (2008)
Publisher : Pusat Penelitian dan Pengembangan BMKG

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1713.289 KB) | DOI: 10.31172/jmg.v9i1.18

Abstract

Sinyal radio frekuensi-ganda yang dipancarkan dari satelit Global Positioning System (GPS) memungkinkan untuk pengukuran jumlah total elektron, disebut sebagai total electron content (TEC), di lapisan ionosfer sepanjang berkas sinyal antara satelit dan penerima GPS. Pengolahan diferensial TEC (dTEC) secara spasial dan slant TEC  menggunakan data jaringan Sumatran GPS Array (SUGAR) dengan memakai perangkat lunak algoritma GAMIT (GPS Analysis at Massachusetts Institute Technology). Sedangkan variasi dan distribusi vertical TEC diolah dengan perangkat lunak matlab7. Hasil analisis menunjukkan adanya variasi nilai TEC baik itu penurunan maupun peningkatan jumlah elektron. Selama kurun waktu bulan Desember 2004 sampai April 2005 di Sumatera terjadi 10 kali gempabumi dengan kekuatatan M ≥ 6.0 dimana 9 gempabumi diantaranya muncul anomali TEC (penurunan nilai TEC dibawah nilai batas bawah) 1 sampai 6 hari sebelum gempabumi terjadi. Anomali TEC ini dapat dipandang sebagai pertanda (precursory signal) yang muncul sebelum terjadi gempabumi. The double-frequency radio signal which is broadcasted by Global Positioning System (GPS) Satellite enables to measure the number of Total Electron Content (TEC). It exists along ionosphere between the signal beam and GPS receiver. The calculation of TEC differential ( dTEC ) and slant TEC use the Sumatra GPS Array ( SUGAR ) network data. It is done by utilizing the GAMIT (GPS Analysis at Massachusetts Institute of Technology) algorithm software. The distribution of variation and vertical TEC are processed by using Matlab 7 Software. The result of the analysis shows the existence of TEC value both the decrease and the increase of electrons number. From December 2004 until April 2005, ten earthquakes occurred in Sumatra with the magnitude M>6.0. Nine of them appeared the TEC anomaly (the decrease of TEC value is below the lower bound) in 1 up to 6 days before the earthquakes stroke. The TEC anomaly is considered as the precursory signal that occurs before the earthquake strikes.
PENENTUAN WAKTU TIBA GELOMBANG-P SECARA OTOMATIS DENGAN METODA SKEWNESS DAN KURTOSIS TERINTEGRASI Hendar Gunawan; Nanang T. Puspito; Gunawan Ibrahim; P. J. Prih Haryadi; Kadnan Kadnan
Jurnal Meteorologi dan Geofisika Vol 13, No 1 (2012)
Publisher : Pusat Penelitian dan Pengembangan BMKG

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (484.527 KB) | DOI: 10.31172/jmg.v13i1.119

Abstract

Penentuan waktu tiba gelombang P sangat penting dalam perhitungan parameter Peringatan Dini Gempabumi (PDG) yaitu periode dominan dan amplitudo pergeseran maksimum yang digunakan untuk memprediksi magnitudo dan lokasi hiposenter. Metodologi statistik orde tinggi yang disebut dengan Integ telah digunakan untuk menentukan waktu tiba gelombang P. Filter bandpass butterworth orde dua dengan frekuensi 0,075-4 Hz diterapkan untuk menghilangkan efek drift dan gangguan gelombang panjang. Proses integrasi sinyal broadband kecepatan dilakukan untuk mendapatkan sinyal broadband pergeseran. Dari perhitungan yang dilakukan pada 68 sinyal broadband kecepatan yang tercatat oleh stasiun CISI, Jawa Barat sepanjang periode 2009-2011 menunjukan tingkat ketelitian yang lebih baik jika dibandingkan dengan metode STA/LTA yang saat ini digunakan di BMKG. Selisih residu rata-rata metoda Integ dengan data acuan BMKG adalah -0.063 detik dengan standar deviasi 0.393 detik dan standar kesalahan 0.048 detik. Hasil ini menunjukan bahwa metoda Integ memiliki tingkat ketelitian yang baik dan dapat digunakan dalam penentuan parameter PDG. Determination of P-wave arrival time is crucial in the calculation of Earthquake Early Warning (EEW) parameters is dominant period and maximum displacement amplitude is used to predict magnitude and hipocenter. The methodology of higher order statistical called Integ used to determine P-wave arrival time. Bandpass filter of second order butterworth with frequency 0.075-4 Hz is applied to eliminate drift effects and long-wave noise. The integration procces   of velocity broadband signal applied to get displacement signal. From the calculations of 68 velocity broadband signals recorded by CISI station, West Java during period 2009-2011 showed a better accuracy compared to the STA/LTA are currently used in BMKG. Difference in average residual of Integ method to reference data of BMKG is -0063 seconds with standard deviation 0,393 seconds and standard error 0,048 seconds. These results indicate that the Integ method has high accuracy and can be used in the determination of EEW parameters.
Implementation of Filter Picker Algorithm For Aftershock Identification of Lombok Earthquake 2018 A. Ardianto; Y.M. Husni; A. D. Nugraha; M. Muzli; Z. Zulfakriza; H. Afif; David P. Sahara; Sri Widiyantoro; Awali Priyono; Nanang T. Puspito; Pepen Supendi; A. Riyanto; Shengji Wei; B. S. Prabowo
Jurnal Geofisika Vol 17 No 1 (2019): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (8338.28 KB) | DOI: 10.36435/jgf.v17i1.397

Abstract

The ability to identify earthquake events that are consistent, efficient and accurate is increasingly needed along with the increase in the amount of data analyzed. In this paper a filter picker algorithm is implemented to identify aftershock events and determination of arrival time automatically, especially for the P wave phase. Here modifications are made in determining the uncertainty of arrival time and there are additional criteria in determining the time of arrival used. The additional criteria are that in a certain time span, there are at least 5 stations determined by the time the filter picker arrives. This is done to minimize identification errors due to local noise and other practical reasons, namely the minimum number of stations to determine the location and other seismological analysis. To test the filter picker algorithm, aftershock data from the Lombok earthquake occurred on July 29 (M 6.4), August 5 (M 7), and August 19 (M 6.3 and M 6.9) 2018. The aftershock data were used for 30 days, from August 4, 2018 to September 4, 2018 using local seismic station in Lombok Island. The results of the filter picker algorithm were evaluated by comparing the number of earthquake events detected and the accuracy of determining the P wave arrival time automatically to the results of manually arriving time. In addition, a comparison of the results obtained from a broadband type seismometer with a short period is used to find out how much influence the type of tool has on its performance results. The results of the comparison with the manual arrival time show that more than 85 percent of the results of the automatic arrival time have a difference below 0.2 seconds. Therefore, it can be said that the filter picker algorithm is quite effective for identifying events and determining the arrival time of P waves. In this paper it is also shown that this algorithm can be used for broad band and short period seismometer sensor, even without the prior correction of instruments.
Co-Authors A. Afnimar A. Ardianto A. D. Nugraha A. Riyanto Awali Priyono B. S. Prabowo David P. Sahara Djedi S. Widarto Elza Surmaini Gunawan Ibrahim Gunawan Ibrahim H. Afif Hadi, Tri Wahyu Hendar Gunawan Hendri Subakti Kadnan Kadnan M. Muzli P. J. Prih Haryadi Pepen Supendi Shengji Wei Sri Widiyantoro Subagyono, Kasdi Sugeng Pribadi Y.M. Husni Z. Zulfakriza