Microwave Radiation Anomaly of Wenchuan Earthquake and Its Mechanism

1. IGARSS’11 Vancouver 2011.7.27 Microwave Radiation Anomaly of Wenchuan Earthquake and Its Mechanism Shanjun Liu Yuntao Ma Institute for GIS/RS/GPS & Digital Mine ResearchNortheastern University, China

2. OUTLINE • Background- • Earthquake and thermal infrared anomaly • Microwave Anomaly Analysis before Wenchuan EQ • Experimental Study on the Anomaly Mechanism • 4. Conclusions

3. 1. BACKGROUND-Earthquake and thermal anomaly 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.

4. Are there anomaly before earthquake? epicenter • 18 days before earthquake • 1 days before earthquake Some authors have reported that there are thermal infrared anomalies appearing in the satellite remote sensing information before earthquake. sea Thermal infrared anomaly before Zhangbei earthquake of China 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.

5. Loess Plateau Tibetan Plateau India Plate Thermal infrared anomaly before Wenchuan earthquake

6. Problem 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.

7. Two way to solve the problems • 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. • A new method is proposed to extract the microwave radiation anomaly before earthquake.

8. 2. Microwave Anomaly analysis before Wenchuan EQ • 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: • The first step • The first step is to eliminate the effect of the terrain. The following formulas are introduced. 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. tiis a day of non-seismic year i, t0is the same day in the earthquake year.

9. 2)The second step 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. is the background value. is the final result after eliminating the influencing of weather

10. 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.

11. RESULTS Apr. 5 Apr. 14 Apr. 10 Longmenshan Fault Epicenter Sichuan Basin May 6 May 11 Apr. 20

12. May 16 May 18 May 12 May 27 May 20 May 22

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

14. 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.

15. 3 Experimental Study on the Anomaly Mechanism 3.1 Experimental Design Acoustic emission(AE) monitoring instrument Infrared spectroradiometer microwave radiometer Infrared thermal imager

16. load head Microwave antenna AE detector Strain gauge Rock sample and the detectors

17. Experimental Result • 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. Microwave load Infrared AE • 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

18. The experiment result indicates that it is possible to use the microwave remote sensing to monitor the fracture of crust, including earthquake.

19. 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.

20. IGARSS’11 Vancouver 2011.7.27 Thanks！

22. Discussion on the Mechanism • 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.

23. Discussion on the Mechanism Shrink Volume increase Fracture Stage I to Stage II Stage III Stage IV Temperature increase due to friction-heat effect Temperature increase due to thermoelastic effect dielectric constant increase due to vacuum volume increase microwave emission decrease AIRT and microwave emission increase again AIRT and microwave emission increase, AIRT and microwave emission are coincident in step