investigation on volcanic activity and sector collapse inducing ......investigation on volcanic...
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Investigation on volcanic activity and sector collapse inducing the
Sunda Strait tsunami in Indonesia
Iguchi, M. (PI in Japanese side) (DPRI, Kyoto Univ.) Nakamichi, H., Yamada, M. (DPRI, Kyoto Univ.) Kaneko, T. (ERI, Univ. Tokyo), Inoue, H., Nagai, M., S. Nakada (NIED)
Kasbani (PI in Indonesian side) (CVGHM) Gunawan, H., Kristianto, Triastuty, H., Karyono, Mulia, I., Kartadinata, N., Prambada, O., Haerani, N., Basuki, A., Hendratno, K., Prayoga, A.S. (CVGHM)
Presenter: Maeno, F. (ERI, Univ. Tokyo)
Project operation
Topic Operation Location
1 Elucidation of growth and collapse processes of Anak Krakatau volcano based on geological and geomorphological analyses
Geological survey Krakatau Islands
2 Elucidation of the process where small scale eruption activities resulted in collapse of the mountains
Examination of seismicity in long-term CVGHM
3 Elucidation of the collapse process of the mountains
Analysis broadband seismogram CVGHM
4 Evaluation of possibility of future collapse
Operation fixed-wing UAV POS
Installation microphone CVGHM
Topic 1: Elucidation of growth and collapse processes of Anak Krakatau volcano based on geological and geomorphological analyses
Japan Fukashi Maeno (ERI)
Takayuki Kaneko (ERI) Masashi Nagai (NIED) Study area:
Krakatau Islands
Indonesia Nugraha Kartadinata (CVGHM) Oktory Prambada (CVGHM)
Objective: Clarify the cause and process of the flank collapse of Anak Krakatau volcano, based on geological and geomorphological data of the volcano.
Geology group
©Digital Globe
11 June 2005
Anak Krakatau Volcano before collapse
Size: ~2.1 km EW ~2.3 km NS Height: > 300 m a.s.l. Lava flows and a central cone
Anak Krakatau Volcano before collapse
All photos were taken in September 2014
Size: ~2.1 km EW and ~2.3 km NS Height: >300 m a.s.l. Lava flows and a central cone
Accumulation of pyroclasts from Strombolian and Vulcanian eruptions
Geological background
Sigurdsson et al. (1991)
Before 1883 After 1883
A young volcanic island growing since 1927
Sudradjat (1982)
Sudradjat (1982)
Migration of vent to SW
Geological background At least 3 small-scale collapses in the past
Sutawidjaja (2002) Sudradjat (1982)
Sudradjat (1982)
19 Dec 2018 22 Dec 2018 25 Dec 2018 27 Dec 2018
28 Dec 2018 31 Dec 2018 2 Jan 2019 3 Jan 2019
24 Dec 2018
30 Dec 2018 2 Jan 2019
Planet Lab Planet Lab
ALOS-2 JAXA Sentinel-Hub Sentinel-Hub Sentinel-Hub Sentinel-Hub
Sentinel-Hub Sentinel-Hub Sentinel-Hub Sentinel-Hub
Evolution of Anak Krakatau (SAR, Optical)
Collapse ⬇
Growth
3.9 µm
11 µm
Activity in 2019: Himawari-8 data (Thermal anomaly) Variation of thermal anomaly in 2018 (only night)
è The eruption began ~13:50 UTC, 22 December 2018. This time is 30-60 min before tsunami arrival around Sunda Strait (~14:30-15:00 UTC). Length of a side is 200 km.
⬆ ︎Continuous thermal anomaly has been detected since the middle of June. No specific higher anomaly toward the eruption.
13:50
13:40
14:00
14:10
14:20
13:30
3.9 µm
11 µm
January December
30-40 min before tsunami arrival
Tsun
ami
Erup
tion
The last eruption before the event was the 13:51 21 Dec.
2018-12-22
1 year
1 day
Sequence of the 2018 event
Eruption plume
UTC 14:30 14:00 16:00 15:00 15:30
Eruption plume
Erup
tion
inte
nsity
Sustained eruption à
Tsunami arrival at coast
13:30 17:00 16:30
Field survey on 14-16 November 2019
Sertung Panjang (Kecil)
Rakata
Anak Krakatau
Pasauran (Carita) ⇔ Krakatau islands • Anak Krakatau • Panjang island
1212 m
© D︎igital Globe Google Earth
11 June 2005 11 January 2019
Before and after the event
Intermittent small-scale explosions are continuing (Surtseyan-type eruption by magma-water interaction)
Loc. 3
Stratified-cross stratified deposits, suggesting origin of pyroclastic surges, consists of main cone
Bread-crust scoria, indicating a product by magma-water interaction
Future works
n Anak Krakatau has collapsed several times through its eruptive history. n Satellite data suggest that a small eruption began at around 13:50
(UTC) 22 Dec 2018, which is 30-40 minutes before tsunami arrival at coasts along Sunda Strait. Then it was followed by the main sustained eruption.
n We found various types of deposits associated with the 2018 collapse-eruption event at Krakatau islands.
n The eruption started with pyroclastic surge generation. n Distribution, facies, and grain characteristics of deposits will be
important clues to constrain the process of 2018 event.
Summary of geological study
• Grain component and size distribution analyses for deposits. • Geochemical analysis of essential products and comparison
with the past products. • Discuss collapse and eruption processes.
Topic 3: Analysis broadband seismogram Elucidation of the collapse process of Anak Krakatau: Landslide movement history estimated from seismic waveforms Yamada, M., Nakamichi, H. (Kyoto Univ.) Mulia, I., Karyono (CVGHM)
12:00 18:30 19:00 21:03 21:30
Not clear
Plume
Tsunami
CCTV
Erupting
Signal lost Eruption? (official)
CCTV Event Seismic Signal Dec. 22 (WIB)
Time of Eruption
0 50km
MDSI
SBJI
SKJI
BBJI
CGJI
CNJI
LEM
CCTB
Sumatra
Jawa
105.35̊ 105.4̊ 105.45̊
−6.15̊
−6.1̊
−6.05̊
0 1 2 3km
SRTGKRA2KRA3
Broadband Shortperiod
100km
200km
20:52 21:02
Long-period waveforms (> 5 s)
0km 20:54 20:56
Vs~2km/s
Data by CVGHM
Time of Eruption
12:00 13:30 18:30 19:00 20:54 20:56 21:03 21:30
Not clear
Plume
Tsunami
CCTV
Erupting
Amplitude increase
Small collapse Large edifice collapse
Eruption? (official)
CCTV Event Seismic Signal
Signal lost
Dec. 22 (WIB)
Residual Surface of the Inversion
103 ˚ 104 ˚ 105 ˚ 106 ˚ 107 ˚ 108−8̊
−7̊
−6̊
−5̊
−4̊
0 50km
MDSI
SBJI
SKJI
CGJI0.2
0.2
0.20.2
0.20.4
The optimal location is Anak Krakatau.
Force in horizontal plane
A B
B
A
Estimation of the Collapsed mass
Stage1 Stage2
We analyzed the near-source seismic data of the 2018 Anak Krakatau volcano eruption
• Origin time 20:56 (local time) • Collapsed from NE à SW, about 1min, low dip angle • Mass 2.5-5.0 × 1011 kg • Small coefficient of friction
n The volcanic eruption may trigger edifice collapse.
n A warning from seismic signals may be possible if infrastructure is well-prepared.
Summary of seismic waveform analyses
Sequence of the 2018 event
Eruption plume
UTC 14:30 14:00 16:00 15:00 15:30
Eruption plume
Edifice collapse 0.1-0.2 km3
13:56 min
Erup
tion
inte
nsity
Sustained eruption à
Eruption start ~ Edifice collapse à Main eruption start
13:30 17:00 16:30
Tsunami arrival at coast
Summary
Issues: Relationship between collapse and eruption. Detail process and mechanism are still problematic. Implication to volcanoes in Japan Evaluation of collapse potential and mass movement will be important.
We investigate volcanic activity and sector collapse inducing the Sunda Strait tsunami on 22 Dec 2018. n Small-scale eruptions had repeated in the eruption day. Satellite data
shows no large eruption before the event but a significant eruption began at around 13:50 (UTC).
n We found deposits from the collapse/eruption event at Krakatau islands. n The eruption started with pyroclastic surge generation. n Seismic waveform inversion suggest that origin time of collapse was
20:56 (local time), collapse direction NE à SW, and collapse duration about 1 min.
n Collapse volume is estimated to be 2.5-5.0 × 1011 kg (~0.1-0.2 km3). n Collapse occurred with an eruption then followed by a main sustained
eruption.