Mt. Merapi Continues to Rumble

Location of Mt. Merapi. Larger map: maps.google.com
Mount Merapi showed some activity early on Sunday morning.

According to Triyono, the officer at the Mount Merapi Observation Post in Ngepos, Srumbung subdistrict, there was rumbling around 04:25–04:35 local time (22:25–22:35 BST; 17:25–17:35 ET).1 Sri Sumarti, head of the Mt. Merapi division at the Center for Research and Technology Development of Geologic Disaster2 (Indonesian: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi; BPPTKG) in Jogja, reported tremors to have started minutes earlier.3
“Tremors were recorded for around 20 minutes at 04:21 local time on Sunday, and our observers began to hear thunder at 04:26,” she said.

Locals were startled by the rumbling, said Ismael, the village leader of Babadan, Dukun Subdistrict, who also claimed “red-coloured material spewed from the mounts [sic] peak” after the rumbling. Observations made from the Mount Merapi Observation Post in Sewukan, Dukun Subdistrict, found billowing smoke, whereas the post in Ngepos was unable to make any visual confirmation because of fog. There were no evacuations.

A reported 12–15 km (7.4–9.3 mile) radius was affected by the ejection of volcanic ash, particularly on the southwest, south, and southeast of the peak. Head of the Data and Information Center of the National Disaster Mitigation Agency (Indonesian: Badan Nasional Penanggulangan Bencana; BNPB) Sutopo Purwo Nugroho said ash fell in subdistricts that included Dukun, Srumbung, Muntilan, Sawangan, and Mungkid. In Jogja itself, however, it seems to have barely registered.

A possible cause may be the pair of earthquakes that hit at 20:33 (14:33 BST; 09:33 ET) and 22:07 (16:07 BST; 11:07 ET) last week on Friday (i.e. April 18). The earlier and bigger earthquake (M5.2)4 occurred 167 km (103.8 miles) south of Jogja, while the later M5.0 earthquake5 occurred 158 km (98.2 miles) south. The two were just 14 km (8.8 miles) apart. By and large, neither was felt on land, with those who did feel them reporting only a minor tremor.6
The BPPTKG was not able to confirm a connection, but did record four tectonic quakes the next day between 08:00 and 20:00. Although, again, there was no confirmation of a connection between these quakes and Merapi’s activity on Sunday, according to Sri.

Mt. Merapi on Saturday morning. Source: https://twitter.com/BPPTKG
There is some conflicting information regarding whether lava was emitted during this period.

Nugroho said that lava flowed as far as 1 km from Merapi’s peak, toward the head of Senowo River. Sri contradicted this assertion, saying no lava had flowed during the activity. In its report, Antara News hedges the aforementioned from Nugroho, stating: “According to the analysis, the lava was not new or juvenile material as the mount has not hade [sic] new magmatic eruption phase.”

Fortunately, Merapi’s status at present remains unchanged. This appears to have been an isolated incident, and as always, the BPPTKG will “continue to monitor and evaluate the conditions of the volcano routinely.”

Notes
1. M. Hari Atmoko, "Mt. Merapi rumbles spewing volcanic material to nearby areas," Antara News, April 20, 2014, http://www.antaranews.com/en/news/93713/mt-merapi-rumbles-spewing-volcanic-material-to-nearby-areas.
2. See also: https://twitter.com/BPPTKG.
3. The Jakarta Post, "Mt.Merapi [sic] spews smoke," The Jakarta Post, April 20, 2014, http://www.thejakartapost.com/news/2014/04/20/mtmerapi-spews-smoke.html.
4. USGS, http://earthquake.usgs.gov/earthquakes/eventpage/usb000pq2c#summary.
5. USGS, http://earthquake.usgs.gov/earthquakes/eventpage/usb000pq5b#summary.
6. Yoga Purnama Putra, "Gempa 5.6 & 5.3 Skala Richter Kembali terjadi di Yogyakarta, Jum’at, 18 April 2014," Pekanbaru.co, http://www.pekanbaru.co/21876/gempa-5-6-skala-richter-kembali-terjadi-di-yogyakarta-jumat-18-april-2014/. Although this report says the first and second earthquakes had magnitudes of 5.6 and 5.3, respectively, we cited USGS's figures, instead, which we believe to be more precise.

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