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Many islands in Indonesia are formed due to the lifting of the seafloor which forms limestone lithology and forms karst morphology. The karst region has a large freshwater potential that accumulates in the underground river system. The existence of an underground river system as a water reservoir is very important in fulfilling the needs of the community, especially in island countries such as Indonesia that have many karst regions. Research to map the position and distribution of underground rivers is carried out by applying geophysical methods. One of the geophysical methods applied is the microtremor method. The working principle of this method is the identification of underground rivers based on Particle Motion method and Time Frequency Analysis (TFA). That analysis resulted in the particles movement direction that perpendicular to the vibration source which is identified as the underground river. The existence of the underground river is then validated based on the TFA parameters of the underground river karst region. The results of the Particle Motion analysis at the research location show the character of the river flow pattern that has a Northeast-Southwestern orientation, and based on TFA there is amplitude continuity in the river flowed area with a frequency range of 4 - 5 Hz and an amplitude of 2,000 dB – 20,000 dB on component Z (vertical).

One algorithm to classify textual data in automatic organizing of documents application is KNN, by changing word representations into vectors. The distance calculation in the KNN algorithm becomes essential in measuring the closeness between data elements. This study compares four distance calculations commonly used in KNN, namely Euclidean, Chebyshev, Manhattan, and Minkowski. The dataset used data from Youtube Eminem’s comments which contain 448 data. This study showed that Euclidian or Minkowski on the KNN algorithm achieved the best result compared to Chebycev and Manhattan. The best results on KNN are obtained when the K value is 3.

Kawasan vulkanik gunung Bromo menarik banyak wisatawan dari seluruh penjuru dunia. Selain wisata pemandangan, wisata edukasi juga banyak diminati terutama oleh pelajar dan mahasiswa. Salah satu edukasi di bidang geosain yaitu dengan mengetahui jenis batuan beserta keterdapatannya. Identifikasi jenis batuan akan menunjukkan komposisi batuan penyusun dan sejarah pembentukan gunungapi. Jenis batuan tersebut didapatkan dengan melakukan studi geologi dan geofisika. Studi geologi meliputi jenis batuan dan identifikasi conto kerucut skoria sedangkan studi geofisika meliputi seismik, resistivitas dan mikrotremor pada beberapa lokasi di area kaldera Lautan Pasir. Hasil studi tersebut dapat dimanfaatkan oleh masyarakat umum yang bertujuan mempelajari tentang gunung Bromo beserta material hasil erupsinya.

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