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A total of 673 earthquakes shook the Indonesian territory during August 2019. 3 of these, 3 of them produced considerable damage.

As reported by Daryono, Head of the Earthquake and Tsunami Mitigation Agency for Meteorology, Climatology and Geophysics (BMKG), through his Instagram account, the total number of tectonic earthquakes during August 2019 was 673 times.

Earthquakes with a significant magnitude, that is, above 5.0 (M> 5.0), occurred 22 times. Earthquakes whose vibrations were easily perceived were 56. Only 3 of these movements were destructive earthquakes.

The first of these major earthquakes happened on August 2, 2019 in southern Banten, with a magnitude of 6.9 and a recorded damage of 7 houses that extended to the districts of Cianjur, West Bandung and Sukabumi.

The second destructive earthquake occurred in Banyuwangi on August 12, 2019, its magnitude was 5.0 and caused multiple minor damages on the beaches of Pancar and Rajegwesi, in Banyuwangi province.

The third of these strong earthquakes took place on August 23, 2019 on Mount Salak, with a magnitude of 4.0. This earthquake caused damage to the homes of several residents in the Nanggung district of Bogor province.

In addition, during the month of August 2019 there was also a swarm earthquake. It is called "swarm earthquake" to a period of seismic activity, located in a geographical area, where the average magnitude is relatively small but the frequency is very high, that is, there are many tremors but most are mild.

The swarm phenomena in Indonesia have occurred several times: in Klangon Madiun (June 2015), Jailolo Halmahera Barat (December 2015) and Mamasa Sulawesi South (November 2018). During the span of the Madiun swarm earthquake, which occurred on August 3, 2019, there were more than 19 earthquakes per day.

The next swarm earthquake occurred southwest of the foot of Salak Mountain from August 10 to 28, 2019. At least 84 movements were recorded for 18 days. This caused some disturbances and that some people moved to the tea plantations.

In some cases, the swarm occurs in volcanic areas, areas that experience stress fields related to the insistence of magmatic activity. But several reports indicate that swarm activity can also occur in non-volcanic areas, areas with fragile rock characteristics, where it is easy for cracks (fractures) to occur.

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BMKG: Selama Bulan Agustus 2019 di Wilayah Indonesia Terjadi Gempa Sebanyak 673 Kali, 3 Gempa Diantaranya Merusak Total kejadian gempa bumi tektonik selama bulan Agustus 2019 terjadi sebanyak 673 kali. Gempa bumi dengan magnitudo signifikan di atas 5,0 (M > 5,0) terjadi sebanyak 22 kali. Sedangkam gempa bumi yang guncangannya dirasakan terjadi sebanyak 56 kali. Selama bulan Agustus 2019 di Indonesia terjadi gempa merusak 3 kali, yaitu; (1) Gempa Selatan Banten pada 2 Agustus 2019 dengan magnitudo M=6,9, yang merusak 7 bangunan rumah yang tersebar di Kabupaten Cianjur, Kabupaten Bandung Barat, dan Kabupaten Sukabumi. (2) Gempa Banyuwangi pada 12 Agustus 2019 dengan megnitudo M=5,0 menyebabkan beberapa rumah rusak ringan di Pantai Pancar dan Rajegwesi, Banyuwangi. (3) Gempa Kaki Gunung Salak pada 23 Agustus 2019 M=4,0 menyebabkan beberapa bangunan rumah warga rusak ringan di Kecamatan Nanggung, Kabupaten Bogor). Selama Bulan Agustus 2019 juga terjadi gempa swarm. Swarm adalah serangkaian aktivitas gempa bermagnitudo relatif kecil dengan frekuensi kejadiannya sangat tinggi dan berlangsung dalam waktu yang relatif lama di wilayah sangat lokal. Fenomena swarm di Indonesia sudah terjadi beberapa kali, seperti aktivitas swarm di Klangon Madiun (Juni 2015), Jailolo Halmahera barat (Desember 2015), dan Mamasa Sulawesi Barat (November 2018). Gempa swarm Madiun terjadi pada 3 Agustus 2019 dimana terjadi gempa lebih dari 19 kali dalam sehari. Selanjutnya adalah swarm juga terjadi di sebelah baratdaya Kaki Gunung Salak pada10 hingga 28 Agustus 2019. Selama sekitar 18 hari terjadi gempa lebih dari 84 kali hingga masyarakat resah dan sebagian mengungsi di perkebunan teh. Patut disyukuri bahwa aktivitas Swarm saat ini sudah mereda. Pada beberapa kasus swarm terjadi di zona gunungapi. Swarm dapat terjadi di kawasan yang mengalami medan tegangan berkaitan dengan desakan aktivitas magmatik. Selain berkaitan dengan kawasan gunungapi, beberapa laporan menunjukkan bahwa aktivitas swarm juga dapat terjadi di kawasan non volkanik. Swarm memang dapat terjadi di kawasan dengan karakteristik batuan yang rapuh sehingga mudah terjadi retakan (fractures). DARYONO

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