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Identifying Temporal Change of Merapi Identifying Temporal Change of Merapi Eruption Type by Satellite SAR Data Eruption Type by Satellite SAR Data Analysis Analysis

Asep SAEPULOH1, Katsuaki KOIKE1, Makoto OMURA2, Masato IGUCHI3

1Department of Life and Environmental Sciences, Kumamoto University 2Department of Environmental Science, Kochi Women’s University 3Disaster Prevention Research Institute, Kyoto University

Study site Study site

INDONESIA

• Mt. Merapi

Landsat ETM+ B:457

Located in Central

Java, Indonesia.

One of 129 the most

active volcanoes.

Detection of Active Volcano Topographical Detection of Active Volcano Topographical Change of Mt. Merapi Change of Mt. Merapi

Photos: Undertoad, 2006

Normal Active Eruption Stage

Photos: Undertoad, 2006

Data:

Ten SAR data set Five sets JERS-1 =>

Intensity

Five sets Radarsat =>

Brightness

• G. MERAPI

DATA SELECTION DATA SELECTION

RADARSAT-1 SAR

Frequency 5.3 GHz Capability HH Polarization Right-looking (North) Range/Azimuth res. 8-9 m

JERS-1

Frequency 1.275 GHz Capability HH Polarization Right-looking (North) Range/Azimuth res. 18 m

Problem Definition

How to detect the volcanic

deposits due to the bad atmospheric condition such as clouds and ashes soon after eruption time?

How to understand the

characteristics of volcanic product detected for each eruption period?

Clouds and ashes cover the volcano make optical sensor prevent to obtain surface condition.

Merapi 2002/05/14

Range Azimuth

Before eruption Merapi 2006/05/17 After eruption

Range Azimuth

The data acquired on May 14, 2002 as an initial condition of Mt. Merapi and on May 17, 2006 as data after the eruption occurred.

Intensity Images of RADARSAT SAR for

• Mt. Merapi

Merapi 2006/05/17

Range Azimuth

Incident wave

Dark portion on the RADARSAT SAR data was represented as uniformity flowing material such pyroclatic flows as settling by gravitational energy

Rough Smooth

www.indahnesia.com & Bronto, 2006

Before eruption

Changed volcanic product, 2002 to 2006 data, shows some new features clearly.

After eruption

Topographic Abrupt Change Detection

Square root of subtraction powered image

Square root of subtraction powered image

• Mt. Merapi

Fault

Geological map of the Yogyakarta sheet. (Rahardjo et al., 1995)

Ratio image Subtraction image

www.indahnesia.com & Bronto, 2006

Lava Pyroclastics

Ratio Image βo Image

Lava flows differ from pyroclatic flows based on different peak histogram from bi-level threshold images Temporal arithmetical calculation and low level feature extraction were used to discriminate volcanic product distribution

SAR Pair Temporal Detection Ten SAR data which are divided into 6 pairs were used to obtain the characteristics of Mt. Merapi volcanic distribution SAR data SAR pair history

Pair Pair of SAR data (yyyy.mm.dd) Area (km2) Distance (km) Azimuth Sensor Modeling S…W I 1996.04.06 1996.11.12 0.8 2.3 F(x)=0.92x-123.76 47.0° JERS-1 II 1996.04.06 1997.02.08 1.0 3.3 F(x)=0.76x-108.8 53.0° JERS-1 III 1998.01.26 1998.07.21 2.0 4.7 F(x)=0.44x-80.38 66.0° JERS-1 IV 1998.08.15 2000.11.08 3.3 4.4 F(x)=0.22x-64.23 78.0° RADARSAT-1 V 2001.02.12 2002.05.14 2.3 3.9 F(x)=0.16x-59.75 81.0° RADARSAT-1 VI 2002.05.14 2006.07.04 1.8 2.2 F(x)=0.15x-58.8 81.3° RADARSAT-1

Result Result

Temporal detection Low level feature extraction

• Binarization
• Region descriptor

Vectorizing Geometric calculation

• Area
• Travel distance
• Azimuth

Geometry of pyroclastic deposit

Temporal Change of Pyroclastic Temporal Change of Pyroclastic Deposits of Mt. Merapi Deposits of Mt. Merapi Characteristics of pyroclastic deposits over ten years observation Pyroclastic flows change of Mt. Merapi

Conclusions Conclusions

• 1. Using SAR amplitude data extraction, some geological

and topographical features are easier to be obtained.

• 2. In ten years observation of SAR data, there are three

characteristics found for pyroclastic flows deposits; coverage area, travel distances and azimuth of the flows.

• 3. The coverage areas and travel distances of volcanic

deposit of Mt. Merapi is scattered by time eruption.

• 4. However, the azimuth of pyroclastic flow deposits

which has changed constantly to one tendency. The products rotated clockwise from the south to the west.