microwave radiation anomaly of wenchuan earthquake and its mechanism.ppt

Institute for GIS/RS/GPS & Digital Mine Research, NEU, P.R. China, www.dgmine.comwww.dgmine.com

Microwave Radiation Anomaly of Wenchuan Microwave Radiation Anomaly of Wenchuan

Earthquake and Its Mechanism Earthquake and Its Mechanism

Shanjun Liu Yuntao Ma

Institute for GIS/RS/GPS & Digital Mine Research

Northeastern University, China

IGARSS’11 Vancouver 2011.7.27

1. Background-

Earthquake and thermal infrared anomaly

3. Microwave Anomaly Analysis before Wenchuan EQ

4. Experimental Study on the Anomaly Mechanism

4. Conclusions

OUTLINE

Since 2000 there are many violent earthquakes happened in the world, such as Sumatra earthquake, Wenchuan earthquake, Haiti earthquake and Japan earthquake. These earthquakes cause many people death and injured.

1. BACKGROUND-Earthquake and thermal anomaly

Some authors have reported that there are thermal infrared anomalies appearing in the satellite remote sensing information before earthquake.

Are there anomaly before earthquake?

18 days before earthquake, the temperature of the sea area was hotter than the land in the night, but 1 days before earthquake the hot area broke the restrict of coastline and moved toward the epicenter of earthquake.

1 days before earthquake 18 days before earthquake

epicenter

sea

Thermal infrared anomaly before Zhangbei earthquake of China

Thermal infrared anomaly before Wenchuan earthquake

India Plate

Tibetan Plateau

Loess Plateau

It is difficult to distinguish the thermal anomaly from the

satellite thermal infrared data due to the disturbance of

cloud weather days.

It is difficult to obtain the real thermal anomaly from the

complicated remote sensing information because of the

influencing of many factors, such as geographical and

weather change etc.

Problem

Two way to solve the problems

2) The microwave remote sensing data is used to analyze the

anomaly instead of the thermal infrared data because it can

penetrate the cloud, so it is better to extract the anomaly

than thermal infrared data.

3) A new method is proposed to extract the microwave

radiation anomaly before earthquake.

Methodology of extracting microwave anomaly

For extracting the microwave anomaly before Wenchuan earthquake a new method is proposed. The method can be divided into two steps:

3)The first step

The first step is to eliminate the effect of the terrain. The following formulas are introduced.

NtrTrTN

ii /)],([)(

1∑

=

= )(),(),( 00 rTtrTtrT −=∆)r(T is the average microwave brightness temperature of pixel r in the

same day of non- earthquake years in the investigated area.

i is the number of non-seismic years, N is the total amount of non-seismic years. ti is a day of non-seismic year i, t0 is the same day in the

earthquake year.

2. Microwave Anomaly analysis before Wenchuan EQ

The second step is to eliminate the influencing of weather condition.

Suppose the whole investigated area is in the same weather conditions, i.e.

the brightness temperature variations of all pixels are in same step. we select

the mean value of four pixels located at the four corners of the investigated

area as the background value. The following formulas are introduced.

2)The second step

4/),()(4

100 ∑

=

∆=∆j

j trTtT )(),(),( 000 tTtrTtrT ∆−∆=∆∆

)t(T 0∆ is the background value.

)t,r(T 0∆∆ is the final result after eliminating the influencing of weather

Through above two steps the influencing of geographical and

weather are eliminated. So we can analyze the microwave

radiation anomaly before Wenchuan earthquake.

Data

AMSR-E data was selected to analyze the microwave anomaly

Frequency: 18.7GHz

Polarization type: vertical

Time range: from Appr.1 to May 30 of each year between 2003

and 2008.

RESULTS Apr. 5 Apr. 10

Sichuan Basin

Longmenshan Fault

Epicenter

Apr. 14

Apr. 20 May 6 May 11

May 12 May 16 May 18

May 20 May 22 May 27

the epicenters of aftershocks were coincident with the anomaly area in spatial position

aftershocks Microwave anomaly

Anomlay Features

1) From 40 days to 2 days before Wenchuan earthquake some

positive microwave anomalies appeared on the surrounding area of

epicenter. The largest increment of microwave brightness

temperature in the investigated area was up to 12K;

2) 1 day before earthquake (May 11, 2008) the anomaly moved

gradually to the epicenter of the earthquake.

3) After the earthquake the anomaly distributed along the

Longmenshan Fault, and the epicenters of aftershocks were

coincident with the anomaly area in spatial position.

3.1 Experimental Design

Infrared thermal imager

Infrared spectroradiometer

3 Experimental Study on the Anomaly Mechanism

microwave radiometer

Acoustic emission(AE) monitoring instrument

Rock sample and the detectors

AE detector

Microwave antenna

Strain gauge

load head

The loading process can be divided into four stages, stage I,II,III and IV. Every sensor signals varies with the load, but the variation features is different.

Microwave shows steady in the stage I, increasing in the stage II, decreasing in the stage III and increasing again in the stage IV. The point A is the early precursor and the point B is the approaching warning of rock failure .

Average infrared radiation temperature (AIRT) shows fluctuating in the stage I, increasing steadily in the stage II, increasing rapidly in the stage III and decreasing in the stage IV. The point C is the early precursor and the point D is the approaching warning of rock failure.

Experimental Result

•The AE shows no signal appears in the stage I, a small quantity in the stage II, increasing in the stage III and plentiful in the stage IV. The plentiful AE signals indicate rock will failure.

•The infrared radiation has the close relationship with the load, but the microwave radiation has the close relationship with the acoustic emission

load

A

0 50 100 150 200 250 300

285.9

286.0

286.1

286.2

286.3

286.4

286.5

286.6

Brig

htne

ss T

empe

ratu

re/?

Time/s

Ⅰ

Ⅱ

Ⅰ

Ⅲ

Ⅰ

Ⅳ

Ⅰ

B Ⅰ Ⅱ

Ⅰ

Ⅲ

Ⅰ

Ⅳ

Ⅰ 0 50 100 150 200 250 300

0

50

100

150

200

250

Load

/kN

Time/s

0 50 100 150 200 250 300-0.02

-0.01

0.00

0.01

0.02

0.03

0.04

0.05

0.06

AIR

T/?

Time/s

Ⅰ Ⅱ

Ⅰ

Ⅲ

Ⅰ

Ⅳ

Ⅰ

C

D

0 50 100 150 200 250 3000

100

200

300

400

500A

E c

ount

Time/s

Ⅰ Ⅱ

Ⅰ

Ⅲ

Ⅰ

Ⅳ

Ⅰ

Microwave

AEInfrared

The experiment result indicates that it is possible to

use the microwave remote sensing to monitor the

fracture of crust, including earthquake.

4. Summary

In order to eliminate the effect of the geography and

weather a new method is proposed to extract the microwave

radiation anomaly before earthquake.

The microwave radiation feature before Whenchuan

earthquake is analyzed. The result shows the microwave

anomaly appeared before 1 day of the earthquake.

The physical simulation experiment shows the microwave

radiation increases in the fracturing stage, it can explain the

microwave radiation anomaly before Wenchuan

earthquake.


IGARSS’11 Vancouver 2011.7.27

According to the Rayleigh-Jeans Law the microwave emission

energy is in direct proportion with emissivity and physical

temperature of the object.

TB=eT

Where TB is the brightness temperature, e is the emissivity, and T is

the physical temperature of the object.

The emissivity e is mainly decided by the dielectric constant. For

rock material it is related to mineral ingredient, water contents, rock

structure etc.

Discussion on the Mechanism


Stage I to Stage II Stage III Stage IV

Temperature increase due to thermoelastic effect

AIRT and microwave emission increase, AIRT and microwave emission are coincident in step

dielectric constant increase due to vacuum volume increase

microwave emission decrease

Temperature increase due to friction-heat effect

AIRT and microwave emission increase again

Shrink Volume increase Fracture

Discussion on the Mechanism

microwave radiation anomaly of wenchuan earthquake and its mechanism.ppt

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