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MEKANIKA PERAMBATAN GELOMBANG TSUNAMI: STUDI KASUS TSUNAMI TELUK PALU DAN SELAT SUNDA TAHUN 2018 Roifatu Diana Zain; Tjipto Prastowo
Jurnal Inovasi Fisika Indonesia (IFI) Vol 11 No 1 (2022)
Publisher : Jurusan Fisika FMIPA Universitas Negeri Surabaya

Abstrak Pemahaman mekanika perambatan gelombang tsunami adalah penting dalam studi mitigasi bencana tsunami. Aspek kinematik menjelaskan fenomena tsunami time delay dan aspek dinamik menjelaskan fenomena tsunami run-up. Time delay dihitung sebagai selisih waktu antara kedatangan gelombang tsunami dan estimasi waktu tiba berdasarkan aproksimasi shallow water dimana tsunami bergerak dengan kecepatan yang hanya bergantung pada kedalaman lokal. Estimasi run-up diuji menggunakan Hukum Green dengan hanya mempertimbangkan efek pendangkalan pantai dan Hukum Green yang telah dimodifikasi dengan menyertakan efek refraksi gelombang tsunami saat mendekati pantai. Tujuan penelitian adalah menguji apakah aspek kinematik dan dinamik perambatan gelombang tsunami berlaku untuk kasus tsunami Teluk Palu dan Selat Sunda pada tahun 2018. Data penelitian diperoleh dari NOAA (lembaga kredibel yang dikelola oleh pemerintah US) dan beberapa publikasi yang relevan. Hasil-hasil penelitian berupa grafik time delay yang menunjukkan bahwa observed travel times lebih besar dibandingkan dengan estimated travel times. Hal ini berarti tsunami datang terlambat ke tepi pantai akibat deformasi fisis dasar laut. Selain itu, juga diperoleh grafik time delay terhadap travel distance, dimana untuk Teluk Palu diperoleh 0,61 sedangkan untuk Selat Sunda, 0,82. Faktor geometri Teluk Palu dan Selat Sunda yang relatif sempit dibandingkan dengan Samudera Pasifik menjadi alasan mengapa tidak sebesar kasus trans-Pasifik seperti temuan penelitian terdahulu. Estimasi run-up berbasis modifikasi Hukum Green memberikan hasil perhitungan yang lebih baik dibandingkan dengan menggunakan Hukum Green yang hanya mempertimbangkan efek pendangkalan, dimana ada peningkatan akurasi estimasi run-up sebesar 2-3 kali lipat. Kesimpulan penting adalah aspek kinematik dan dinamik perambatan gelombang tsunami masih berlaku untuk tsunami Teluk Palu dan Selat Sunda dengan penyimpangan terbatas karena faktor geometri lokasi kejadian. Kata Kunci: tsunami time delay, travel time, tsunami run-up, shallow water, hukum Green Abstract Understanding of mechanics of tsunami wave propagation is important for hazard mitigation study. Kinematic aspects explain tsunami time delay and dynamic perspectives predict tsunami run-up. Time delay is defined as the time difference between recorded arrival time at a particular station and estimated arrival time on the wave arrival calculated by shallow-water approximation where tsunamis propagate at a depth-dependence speed. Run-up was estimated using basic Green’s law, considering only shoaling effects and modified Green’s law, incorporating effects of wave refraction into calculation when a tsunami approaches coastal lines. The aim of the study is to examine whether kinematic and dynamic aspects of tsunami propagation remain valid for the 2018 Palu Bay and Sunda Strait tsunamis. The data were obtained from NOAA (a credible institution managed by the US govt) and some relevant publications. The results were given in graphs of time delay, where observed travel times are larger than estimated ones for both cases. It follows that a tsunami arrives late at the coasts due to speed reduction by bottom deformation. Further, it was found that time delay is a function of travel distance with 0,61 for the Palu Bay and 0,82 for the Sunda Strait. The geometry of Palu Bay and Sunda Strait is relatively narrow compared to the Pacific, leading to a reduction in for both events in comparison to the previous findings. Modified run-ups provided better estimates than those calculated from the only basic shoaling, where an increase of 2-3 times higher in accuracy was confirmed. Both aspects of tsunami propagation for Palu Bay and Sunda Strait tsunamis remain valid despite some deviation owing to the local geometrical factors. Keywords: tsunami time delay, travel time, tsunami run-up, shallow water approximation, Green’s law

ANALISIS SEISMISITAS DAN POTENSI BAHAYA BENCANA SEISMIK DI WILAYAH SELATAN PULAU SUMATERA Intan Novia Sari; Tjipto Prastowo
Jurnal Inovasi Fisika Indonesia (IFI) Vol 11 No 2 (2022)
Publisher : Jurusan Fisika FMIPA Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/ifi.v11n2.p12-19

AbstrakPotensi bencana gempa di wilayah selatan Sumatera dapat dipelajari melalui studi seismisitas wilayah denganmenghitung ????-value untuk mendiskripsikan level seismisitas dan ????-value untuk mediskripsikan stres batuan geologibawah permukaan. Data penelitian ini adalah statistik magnitudo antara 3,5 ≤ ????w ≤ 8,4 selama tahun 1970-2021 dengankedalaman gempa mencapai 640 km yang bisa diakses melalui laman https://earthquake.usgs.gov/earthquakes/search/.Perhitungan ????-value dan ????-value dilakukan dengan membagi wilayah selatan Sumatera menjadi Zona 1, Zona 2, danZona 3 dengan hasil-hasil untuk Zona 1: ???? = 6,40 dan ???? = 0,83; Zona 2: ???? = 6,78 dan ???? = 0,91; dan Zona 3: ???? = 6,15dan ???? = 1,05. Berbeda dengan nilai ???? dan ????, anomali ???? tidak dinyatakan sebagai angka melainkan dalam bentuk petavariasi spasial ????-value. Analisis hasil-hasil perhitungan ???? dan ???? untuk ketiga zona seismik menunjukkan bahwaseismisitas Zona 2 paling tinggi karena aktivitas seismo-tektonik sepanjang transisi zona subduksi Sumatera menujuzona subduksi Jawa. Seismisitas Zona 1 juga relatif tinggi dipicu oleh aktivitas serupa sepanjang zona subduksi dekatPalung Sumatera dan Sesar Besar Sumatera. Hal ini berarti wilayah barat Sumatera bagian selatan lebih rentan terhadappotensi bencana gempa tektonik. Analisis variasi spasial ????-value menemukan wilayah selatan Sumatera dengan ????-valueyang rendah bertepatan dengan saat gempa besar yang memicu gelombang tsunami pada tanggal 12 September 2007.Hasil-hasil penelitian ini sama dengan temuan terdahulu yang relevan dengan studi seismisitas Pulau Sumatera.Kata Kunci: seismisitas wilayah selatan Sumatera, ????-value, ????-value, anomali ????-value AbstractThe potency for eartquakes hazards in southern Sumatera can be examined by calculating ????-value used todescribe seismicity and ????-value used to describe subsurface rock stress. The data for this study are earthquake momentmagnitudes between 3,5 ≤ ????w ≤ 8,4 during the years of 1970-2021 with depths reaching to 640 km accessed athttps://earthquake.usgs.gov/earthquakes/search/. Calculation was performed by dividing the southern Sumatera intoZone 1, Zone 2, and Zone 3 with the results were for Zone 1: ???? = 6.40 and ???? = 0.83; Zona 2: ???? = 6.78 and ???? = 0.91; andZona 3: ???? = 6.15 and ???? = 1.05. Different from ????-value and ????-value, the ???? anomaly was not represented in numbers butit was given in the spatial variation of ????-value. Analysis showed that seismicity in Zone 2 is the highest due to seismotectonic activity along transition from Sumatera to Java subduction zone. Seismicity in Zone 1 is also relatively hightriggered by similar activity along the subduction zone near the Sumatran Trench and the Great Sumatran Fault. Itmeans that the western part of the southern Sumatera is more vulnerable to tectonic earthquake potential. The analysisof spatial variations of the ????-value found that regions of low ????-value corresponded to a large earthquake that generatedtsunami on September 12, 2007. The current results are consistent with previous finding for Sumatera seismicity.Keywords: southern Sumatera seismicity, ????-value, ????-value, ????-value anomaly

IDENTIFIKASI SESAR GRINDULU DENGAN MEMANFAATKAN METODE GRAVITASI Hikmatul Maulidah; Tjipto Prastowo; Arie Realita
Jurnal Inovasi Fisika Indonesia (IFI) Vol 11 No 2 (2022)
Publisher : Jurusan Fisika FMIPA Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/ifi.v11n02.p20-27

AbstrakSesar aktif merupakan salah satu sumber potensial pemicu gempa tektonik di wilayah selatan Jawa Timur,dimana Pacitan merupakan kabupaten dengan tatanan geologi yang didominasi oleh busur pengunungan selatan.Identifikasi kehadiran dan karakteristik Sesar Grindulu di Kabupaten Pacitan adalah penting sebagai bagian dari studimitigasi bencana seismik. Proses identifikasi kehadiran dan karakteristik sesar tersebut memanfaatkan metode gravitasiuntuk menentukan posisi geografis, orientasi dan tipe Sesar Grindulu. Data penelitian berupa distribusi anomali gravitasiyang diperoleh dari satelit TOPEX dengan beberapa koreksi untuk mendapatkan Complete Bouguer Anomaly (CBA).Teknik pemfilteran kontinuitas ke atas diterapkan untuk memisahkan anomali regional dan anomali lokal sehingga bisadigunakan untuk mengetahui orientasi sesar. Teknik Second Vertical Derivative (SVD) diterapkan untuk mengetahuilokasi dan tipe sesar. Analisis semua teknik yang diterapkan dalam penelitian ini memberikan kesimpulan bahwa posisiSesar Grindulu adalah 111,1o – 111,3o BT dan 8,1o – 8,2o LS dengan orientasi arah timur laut–barat daya (NE-SW).Area timur laut identik dengan wilayah utara Kabupaten Pacitan yang didominasi batuan dengan densitas rendah dandiduga memotong jalur utama Sesar Grindulu di perlintasan Sungai Grindulu. Area barat daya identik dengan wilayahselatan Kabupaten Pacitan yang didominasi oleh batuan dengan densitas relatif tinggi karena wilayah selatan Pacitandipengaruhi oleh aktivitas magmatik busur pengunungan selatan Pulau Jawa. Interpretasi hasil terapan teknik SVD pada5 slicing anomali lokal menunjukkan bahwa Sesar Grindulu merupakan sesar dengan kombinasi tipe turun dan geser.Temuan penelitian ini bermanfaat sebagai kajian potensi bencana dan upaya pengurangan risiko bencana di Pacitan. Kata Kunci: Pacitan, Sesar Grindulu, metode gravitasi, TOPEX, kontinuitas ke atas, koreksi CBA, SVD AbstractActive faults have prompted one of potential sources for tectonic earthquakes in the southern regions of East Java,where Pacitan is a region of interest with a geological setting being dominated by the Java southern mountain arc.Identification of the presence and characteristics of Grindulu Fault in Pacitan is vital for seismic hazard mitigation study.In this study, such identification involved the use of gravity method to determine geographical positions, orientation andfaulting type of the Grindulu. The data included gravity anomaly distribution obtained from TOPEX satellites with somelocal corrections towards Complete Bouguer Anomaly (CBA). A filtering technique called upward continuation was usedto separate regional anomaly from local one in order to determine fault orientation. A Second Vertical Derivative (SVD)technique was also used to determine the Grindulu locations and faulting type. Analysis of the applied techniques showedthat the Grindulu is located at 111.1o – 111.3o E and 8.1o – 8.2o S with its NE-SW direction. We found that the northeaststudy area is identical to the northern Pacitan dominated by rocks of low-density across the Grindulu at the Grindulu River.The southwest area is dominated by rocks of high-density as the southern region is much influenced by magmatic activityof the southern mountain arc. The results derived from the SVD technique applied to 5 slicings on the local anomalyshowed that the Grindulu is a combination of normal and strike-slip faults. The current results are useful for examinationof seismic threat potensial hence disaster risk reduction in Pacitan. Keywords: Pacitan, Grindulu Fault, gravity method, TOPEX, upward continuation, CBA, SVD

Development of Multi-Representation Test As A Solution to Train High-Order Thinking Skills High School Students in Newton’s Law Hidayah Zuliana Puspitaningrum; Wasis; Tjipto Prastowo
IJORER : International Journal of Recent Educational Research Vol. 2 No. 1 (2021): January
Publisher : Faculty of Teacher Training and Education Muhammadiyah University of Makassar

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.46245/ijorer.v2i1.76

This research aims to develop a multi-representation based test instrument that can be used to measure students' higher-order thinking skills, especially in Newton's law material. development procedures used the Plomp development model, the stages were design, construction/ realization, test, evaluation, revision, and implementation. The subjects in this study were 36 students of class X at one of High School in Surabaya. At the implementation stage, tests were given to students and analysed using Rasch analysis with help of Winstep software. The multi-representation test instrument in question was a question in the form of an essay with a representation model consisted of visual, verbal, and mathematical representations adapted to the cognitive domain of Bloom's taxonomy of higher-order thinking. Data collection techniques were validation of instruments and tests. The results of this study were 9 items of valid test instruments based on logical validity and empirical validity and a reliable instrument based on calculations using the Alpha Cronbach equation. Based on the results of this research can be concluded that multi-representation test can be train high order thinking skills students. Study with multi-representation test is expected to be able to make students are easier to develop high order thinking skill, in this research students can be categorized as having sufficient high-order thinking skills.

Analisis Kepuasan Workshop Guru Penggerak Online di Trenggalek: Mengoptimalkan Keterampilan Penerbitan Ilmiah Binar Kurnia Prahani; Wasis Wasis; Tjipto Prastowo; Titin Sunarti; Hanandita Veda Saphira
Bubungan Tinggi: Jurnal Pengabdian Masyarakat Vol 4, No 4 (2022)
Publisher : Universitas Lambung Mangkurat

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20527/btjpm.v4i4.6446

Banyak guru kini terdorong oleh kewajiban menerbitkan karya ilmiah untuk memperjuangkan kenaikan pangkat, khususnya di Trenggalek. Kegiatan Pengabdian kepada Masyarakat (PkM) ini dilaksanakan sebagai solusi atas permasalahan tersebut oleh mitra yang telah terbukti efektif dalam memberikan pelatihan penulisan artikel ilmiah/akademik kepada para pendidik guru khususnya di Kabupaten Trenggalek. PKM ini akan meningkatkan keterampilan maupun kemampuan para guru penggerak agar semakin terlihat dan akan berdampak positif langsung terhadap peningkatan kualitas pengajar di Provinsi Trenggalek khususnya penulisan ilmiah. Currently, especially in Trenggalek province, many motivated teachers need help to get promoted due to the obligation to publish academic papers. These findings reveal that teachers lack the knowledge and competence to prepare for scientific work. This community service activity was carried out as a solution to the problem of partners who have proven effective in providing training in writing scientific articles for teacher educators, especially in the Trenggalek Regency. This PKM will make the achievements of driving instructors more visible and will positively impact improving the quality of instructors in Trenggalek, especially in scientific writing.

ANALISIS POTENSI BAHAYA BENCANA SEISMIK DAN KERENTANAN WILAYAH NTB DAN NTT Asri Zakiyah Al-Fakhiroh; Tjipto Prastowo
Jurnal Inovasi Fisika Indonesia (IFI) Vol 12 No 1 (2023): Vol 12 No 1
Publisher : Jurusan Fisika FMIPA Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/ifi.v12n1.p75 - 87

Abstrak Upaya pengurangan risiko bencana seismik bisa dilakukan melalui analisis potensi bahaya dan kerentanan wilayah terhadap bencana seismik berbasis perhitungan parameter dan yang mendiskripsikan level seismisitas dan akumulasi stres batuan bawah permukaan. Studi kasus dalam penelitian ini adalah Provinsi NTB dan NTT dengan data gempa dari katalog USGS antara 1970-2021 dan magnitudo 3,1 ≤ ≤ 8,3 serta kedalaman sumber mencapai 640 km. Kedua parameter diperoleh dari hukum Gutenberg-Richter dan pendekatan maximum likelihood dengan memanfaatkan distribusi frekuensi-magnitudo (FMD) untuk 4 zona seismik yang merepresentasikan kedua provinsi dan kedua sumber pemicu gempa, yaitu Flores Backarc di utara dan zona megathrust di selatan kedua provinsi. Kurva FMD menunjukkan bahwa nilai antara 8-9 dengan rata-rata 6,6 refleksi dari seismisitas dan seismicity rate yang tinggi sedangkan nilai antara 1,01-1,21 indikator mayoritas kejadian gempa adalah moderate magnitudes (4,5 ≤ ≤ 7,0). Meski gempa besar jarang terjadi, namun jalur sesar Flores Backarc berada di Laut Flores yang memanjang dari ujung barat sampai timur wilayah perairan utara NTB dan NTT sehingga potensi pembangkitan gelombang tsunami akibat aktivitas Flores Backarc tetap ada seperti saat gempa 7,8 memicu tsunami Flores 1992. Demikian pula, gempa kuat 8,3 berpusat di perairan selatan NTB memicu tsunami Sumba 1977. Histogram gempa terhadap kedalaman menunjukkan bahwa mayoritas kejadian merupakan shallow events dengan rata-rata kedalaman sumber 35-40 km. Dengan seismisitas tinggi, mayoritas sumber dangkal dan beberapa kali diguncang gempa bawah laut baik di utara maupun selatan, maka kerentanan wilayah NTB dan NTT terhadap bencana seismik perlu diwaspadai. Kata Kunci: : seismisitas, kerentanan wilayah, NTB dan NTT, a-value, b-value Abstract Seismic risk reduction can be peformed by analyzing hazard potential and vulnerability to seismic disasters by calculating parameters and , describing seismicity and stress in subsurface structure. This study examines NTB and NTT vulnerability with the data from USGS between 1970-2021, magnitudes of 3.1 ≤ ≤ 8.3 and source depth of up to 640 km. The parameters were derived from the Gutenberg-Richter law and the maximum likelihood approach by utilizing magnitude-frequency distribution (FMD) for 4 seismic zones to accommodate the provinces and two sources of earthquake: Flores Backarc to the north and a megathrust zone to the south of the provinces. The FMD curves for all seismic zones show that -value ranges from 8-9 with average 6.6 reflecting a high rate of seismicity while -value varies between 1.01-1.21 indicating the majority of events occur at moderate magnitudes (4.5 ≤ ≤ 7.0). Although large earthquakes rarely occur, Flores Backarc extends from the western to the eastern tip of the provinces’ northern waters so that tsunami generation due to sesar activity remains possible, as it occured when the 7.8 earthquake triggered the 1992 Flores tsunami. Likewise, a strong 8.3 earthquake centered in the southern water of NTB triggered the 1977 Sumba tsunami. The histogram against depth shows that most events occur at shallow sources with an average depth of 35-40 km. With high seismicity, many sources are shallow and several times hit by earthquakes on the sea in the northern and southern waters, the vulnerability of the NTB and NTT regions needs to be evaluated. Keywords: seismicity, vulnerability area, NTB and NTT, a-value, b-value

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