Post on 05-Jul-2015
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.
Institute for GIS/RS/GPS & Digital Mine Research, NEU, P.R. China, www.dgmine.comwww.dgmine.com
IGARSS’11 Vancouver 2011.7.27
Institute for GIS/RS/GPS & Digital Mine Research, NEU, P.R. China, www.dgmine.comwww.dgmine.com
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
Institute for GIS/RS/GPS & Digital Mine Research, NEU, P.R. China, www.dgmine.comwww.dgmine.com
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