ANALYSIS OF INDIAN REMOTE SENSING SATELLITE DATA FOR SIKKIM EARTHQUAKE (18 SEPT 2011)

Earthquake Details (Source: USGS)

Date Earthquake EpicentreSunday, September 18, 2011 at 06:10:48 PM at epicentre

6.9 magnitude 27.723°N, 88.064°E19.7 km (12.2 miles)68 km (42 miles) NW of Gangtok, Sikkim, India

Sunday, September 18, 2011 at 06:41:57 PM at epicentre

4.8 magnitude 27.446°N, 88.391°E20 km (12.4 miles)25 km (15 miles) WNW of Gangtok, Sikkim, India

Sunday, September 18, 2011 at 07:24:18 PM at epicentre

4.6 magnitude 27.377°N, 88.266°E20.1 km (12.5 miles)34 km (21 miles) W of Gangtok, Sikkim, India.

Major effected areas in India : Entire Sikkim (Mangan, Chungthang, Singtam, Gangtok etc.), North Bengal (Darjeeling, Kalimpong etc.)

Details of analysis

• Pre and Post-earthquake Satellite data (optical and microwave) were acquired to assess the damage caused by the earthquake (Table 1).

• Optical data received within 24 hours were covered with cloud.

• All the microwave data (Table 1) acquired by NRSC and International charter were analysed for damage assessment. But microwave data could not be interpreted for damage and landslides because of foreshortening and layover effects due to ruggedness of the terrain.

• The latest cloud free IRS data sets were available on 29 and 30, September (Table 1) and the same were analysed for mapping the landslides which occurred after the event.

• Total 354 new landslides were mapped using pre and post CARTOSAT-1 stereo data sets.

Table 1Country Sensor Type Satellite Date of Acquisition Remark

India Optical Cartosat -2 (Mono) 19-sept-2011 Cloudy

India Optical Resourcesat-2 LISS 4 (Mono) 19-sept-2011 Cloudy

India Optical Resourcesat-2 AWiFS 19-sept-2011 Cloudy

Canada Microwave Radarsat-2 (C-band) 19-sept-2011 Layover and foreshortening effect because of terrain

India Microwave RISAT-2 (X-band) 20-sept-2011 Layover and foreshortening effect because of terrain

Germany Microwave TerraSAR-X (X-band) 21-sept-2011 Layover and foreshortening effect because of terrain

India Optical Cartosat 2A 23-sept-2011 Cloudy

India Optical Cartosat-1Cartosat-2AResourcesat-2

24-sept-2011 Cloudy

India Optical Cartosat-1 29-sept-2011 Partly cloudy

India Optical Cartosat-2B 30-sept-2011 Mostly cloud free

India Optical Resourcesat-2 LISS-IV Mx 03-oct-2011 Partly cloudy

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NADOM

BRANG

LACHEN

LACUNG

LINGMORALANG

GEZING

BHENOL

THANGGU

SINGTAM

DONGKUNG

SAKKYONG

PHENGTANG

CHUNGTHANG

NAYA BAZAR

Mangan

Namchi

GANGTOK

Synoptic view of Sikkim from Resourcesat-1 LISS III

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0 8 16 24 324Kilometers

Area analysed for post-earthquake landslides using Cartosat-1 data of 30-sept-2011

Earthquakeepicentre

Satellite image shown here is acquired on 13-apr-2005

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NADOM

BRANG

LACHEN

LACUNG

LINGMORALANG

GEZING

BHENOL

THANGGU

SINGTAM

DONGKUNG

SAKKYONG

PHENGTANG

CHUNGTHANG

NAYA BAZAR

Mangan

Namchi

GANGTOK

Landslide inventory in Sikkim after the earthquakeDetails:Date of event: 18 september 2011Date of cloud free data acquisition: 29, 30 september 2011Type of data: Cartosat-1 and Cartosat-2bNo. of landslides identified: 354 new and 48 old landslides

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0 8 16 24 324Kilometers

LegendOld landslidesNew landslides

See figure 1

See figure 2

See figure 3

See figure 4

See figure 5

88°50'0"E88°40'0"E88°30'0"E88°20'0"E88°10'0"E

28°1

0'0"N

28°0

'0"N

27°5

0'0"N

27°4

0'0"N

27°3

0'0"N

27°2

0'0"N

27°1

0'0"N

See figures 1 to 5 for illustrations

Chungthang

Post-earthquake Cartosat – 1(30-Sept-2011)

Reactivatedlandslides

Pre-earthquake Cartosat – 1(22-March-2011)

Lachen ChuRiver

Cloud Cloud

New Landslides

New Landslides

Road Chungthang to

LachenOldLandslide

Figure 1

Landslides near to road

Road from Nadom to

Chungthang

New Landslides

New Landslide

New Landslides

TistaRiver

Figure 2

Pre-earthquake Cartosat – 1(22-March-2011)

Post-earthquake Cartosat – 1(30-Sept-2011)

Landslides near to road

Newlandslides

Newlandslides

Cloud

Chungthang

Road towards Lachung

Newlandslides

LachungRiver

Cloud

Figure 3

Pre-earthquake Cartosat – 1(22-March-2011)

Post-earthquake Cartosat – 1(30-Sept-2011)

Landslides near to road

Hydelpower site

Newlandslides

Oldlandslides

Tist

a River

Figure 4

Pre-earthquake Cartosat – 1(22-March-2011)

Post-earthquake Cartosat – 1(30-Sept-2011)

Cloud

Cloud

Newlandslides

Newlandslides

Figure 5

Pre-earthquake Cartosat – 1(22-March-2011)

Post-earthquake Cartosat – 1(30-Sept-2011)

Landslides near to road