jul. 29, 2011igarss 2011 1 [3118] relation between rock failure microwave signals detected by amsr-e...

Jul. 29, 2011 IGARSS 2011 1

[3118]RELATION BETWEEN ROCK FAILURE MICROWAVE SIGNALS DETECTED BY AMSR-E AND A DISTRIBUTION OF RUPTURES GENERATED BY SEISMIC ACTIVITY

Takashi MaedaJapan Aerospace Exploration Agency,Earth Observation Research Center

Tadashi TakanoNihon University

IGARSS 2011 2Jul. 29, 2011

Contents

Introduction

Methodology

Latest Analysis Results

Conclusion

IGARSS 2011 3Jul. 29, 2011

Detection of microwave signals generated by rock failures in a laboratory

Simulation of detection capability of rock failure microwave signals using a satellite-borne microwave

sensor

Detection of microwave signals generated by rock failures in a field test

Algorithm development for a satellite-borne microwave sensor to detect rock failure microwave

signals and case studies for some earthquakes

(1) Maki, K. and T. Takano et al. , J. of the Seismological Society of Japan, 2006.

(3) Takano, T. and T. Maeda, IEEE Geoscience and Remote Sensing Letters, 2009.

(4) Maeda, T. and T. Takano, IEEE Trans. on Geoscience and Remote Sensing, 2008.

(5) Maeda, T. and T. Takano, IEEE Trans. on Geoscience and Remote Sensing, 2010.

(2) Takano, T. and T. Maeda et al. , IEEJ Trans. FM, 2009.

Today’s topic

IGARSS 2011 4Jul. 29, 2011

Contents

Introduction

Methodology


Conclusion

IGARSS 2011 5Jul. 29, 2011

Methodology (1) What area do we analyze?

Synthetic Aperture Radar (e.g. ALOS/PALSAR)

Earth’s surface

SAR can detect an area where the land surface was deformed by seismic activity.

However, due to its poor time resolution, it cannot determine by what the land surface was deformed, preslips, a main shock or aftershocks.

IGARSS 2011 6Jul. 29, 2011


Earth’s surface

Rock failures

In such an area, rock failures are likely to occur extremely near the land surface. Microwave signals generated by these rock failures should be emitted into free space without attenuation in the ground.

IGARSS 2011 7Jul. 29, 2011


Earth’s surface

Additionally, once cracks appear in the ground, rock failure microwave signals in the ground, which are caused by aftershocks, should be more easily emitted into free space because cracks act as waveguides.

Accordingly, we focus on an area where severe land surface deformations were detected by InSAR rather than an epicenter.

IGARSS 2011 8Jul. 29, 2011

Methodology (2) Microwave radiometer AMSR-E

It measures microwave signal power (PR) [W] from the atmosphere and the Earth’s surface as a brightness temperature (TB) [K].

The relationship between PR and TB is TB = PR / (k B).

*k: Boltzmann constant, B: Receiver’s bandwidth [Hz]

IGARSS 2011 9Jul. 29, 2011

Methodology (3) Which frequency do we analyze?

Frequency characteristic of emitted microwave signal depends on objectives.

300 MHz 2 GHz 22 GHz

Frequency characteristic of rock failure microwave signals:

23.8 GHz6.9 GHz 10.65 GHz 18.7 GHz ・・・Strong attenuation by water vapor in the atmosphere

Too poor spatial resolution and interference by human activity(e.g. wireless communication)

We analyze brightness temperatures of vertically and horizontally polarized signals at 18.7 GHz (T18V and T18H) in order to detect rock failure microwave signals.

IGARSS 2011 10Jul. 29, 2011

Methodology (4) How do we analyze T18V and T18H?When we define a 1 deg x 1deg rectangular area in latitude and longitude as a target area, AMSR-E observes there almost every night since June 2002.

Local and simultaneous increase of T18V and T18H sometimes appears.From experimental results, response for rock failure signal is also likely to have the similar feature.

T18V T18H

IGARSS 2011 11Jul. 29, 2011

0.05o

Methodology (5) How do we analyze T18V and T18H?

Accordingly, we investigated (1) where (2) when (3) how often during the entire observation periodlocal and simultaneous increases of T18V and T18H appeared in the target area.

10,201 pixels x 4 directions = 40,804 combinations

101 pixels (1 pixel = 0.01o)

101

pixe

lsTarget area

For 40,804 combinations, we investigated time variation of S18 during the entire observation period.

IGARSS 2011 12Jul. 29, 2011

Methodology (6)

3

How many combinations’ S18 became abnormally large on each day?

93/31/2010

Time variation of S18 for a certain combination:

CDF in gamma distribution:

)(

)/,(),0(

k

xkxF

We regard S18 as a gamma-distributed variable because it is always larger than 0. Here, we defined S18 which meets CDF(0, S18) ≥ 0.9974 as an `abnormally large’ value.

0.9974 is corresponding to CDF( , ) in a normal distribution. 3 3

IGARSS 2011 13Jul. 29, 2011

Methodology (6’)

3

Pre-processing: screening of combinations

93/31/2010

Time variation of S18 for a certain combination:

In which combinations did S18 become largest during 1 month centered on the main shock day when we focus only on the similar period in each year?

m1 m1 m1 m1 m1 m1 m1m1

Main shock

― Actually, after screening only combinations which meets this condition, we investigated how many combinations’ S18 became `abnormally large’ on each day.

IGARSS 2011 14Jul. 29, 2011

Contents

Introduction

Methodology


Conclusion

IGARSS 2011 15Jul. 29, 2011

Main shock (2/27/10)Santiago

Concepcion

Epicenter

Target area

Analysis Results (1) – 2010 Chile EQ

How many combinations’ S18 became `abnormally large’ on each day?

8 years

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2/20/10

Main shock (2/27/10)

S18 values became `abnormally large’ in the largest portion of the target area on 2/20/10 (7 days before the EQ).

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δ18 = S18max / S18mean ; In the area with the high δ18 values, S18 values hardly became `abnormally large’. This means the detected phenomenon was extremely rare during the entire observation period.

The area where the land surface was severely deformed coincides with that where S18 values became `abnormally large’.

IGARSS 2011 18Jul. 29, 2011

Contents

Introduction

Methodology


Conclusion

IGARSS 2011 19Jul. 29, 2011

Conclusion We analyzed the data of AMSR-E to detect rock failure signals associated

with an earthquake.

We focused on an area where the land surface severely deformed rather than an epicenter.

We investigated how large was the potion of the target area where S18 became `abnormally large’ on each day during the observation period.

In this presentation, we illustrated the analysis results for the 2010 Chile Earthquake.

We detected the portion began to enlarge before a main shock, became largest around the main shock, and shrank with the termination of aftershock activity (as we detected the similar phenomena for other earthquakes).

When S18 values became `abnormally large’ in the largest portion of the target area, the portion coincided with the area with severe land surface deformations.

IGARSS 2011 20Jul. 29, 2011

Thank you for your attention!

jul. 29, 2011igarss 2011 1 [3118] relation between rock failure microwave signals detected by amsr-e...

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