“Hu-Xi Fault” Is Found By Remote Sensing Li Xian- hua1,2,3

1Research center of Remote Sensing and spatial Information Science

Shanghai University Shanghai, China

2Joint Laboratory of Geosciences Information Academy of Sciences and The Chinese University of Hong

Kong Hong Kong, China

3Shanghai Jiaotong University Shanghai, China

Yi jin-yuan1,4,6, Liu Xue-feng1 , Gu Peng-shou5 ,Lin Hui2 4Shanghai Earthquake Administration,

Shanghai China 5Shanghai Acdemy of Geological Survey

Shanghai , China 6Hangzhou Normal University,

Hangzhou, China

Abstract—The distributing map of surface reflectivity of Shanghai city and its adjacent areas is generated by MODIS remote sensing image. According to the surface spectrum features of this area and the changing characters of surface reflectivity caused by MODIS pixels, we explain the distributing map of surface reflectivity as follows. In the fifth wave band of MODIS, the distributing map of surface reflectivity distinctly shows that there is a deep and spacious fault. The fault is 180 km in length from north to east. The north place is the Wusong in the Yangtze River Estuary and the south place is Zapu around the Hangzhou bay. The widest place and the narrowest place are approximately 10-12 km and 6-8 km in width, respectively. We name it “Hu-Xi fault”. Our conclusions are supported by the aeromagnetic data. We also analyze the changing characters of surface reflectivity in the section plane and the results prove the existence of this “Hu-Xi fault”. On the same distributing map of surface reflectivity, we can find the other spacious fault information. Our conclusions are supported by the other aeromagnetic data. According to the surface spectrum features and the changing characters of surface reflectivity, we can find out the other spacious fault information.

Keywords-MODIS; surface reflectivity; Hu-Xi fault; The section map of surface reflectivity

I. INTRODUCTION Remote sensing image analyzing underground buried

structure is mature and widely used technology, but no obvious signs of large-scale underground hidden faults in the Shanghai area were found in the past similar work of geological remote sensing( Figure 1 is ETM false color composite image of Shanghai. The resolution of the image is 10m. The fault is not shown in the Figure.). In this paper, the distribution map of surface reflectivity of Shanghai city and its adjacent areas is generated by MODIS remote sensing image (any phase can be) with resolution of 500 meters. According to the surface spectrum features of this area and the changing characters of surface reflectivity caused by MODIS pixels, we explain the distributing map of surface reflectivity as follows. In the fifth wave band of MODIS, the distributing

map of surface reflectivity distinctly shows that there is a deep and spacious fault. The fault is 180 km in length from north to east. The north place is the Wusong in the Yangtze River Estuary and the south place is Zapu around the Hangzhou bay. The widest place and the narrowest place are approximately 10-12 km and 6-8 km in width（Figure 2）, respectively. We name it “Hu-Xi fault”.

Our conclusions are supported by the aeromagnetic data [3,

4] (Figure 4, The new construction activity diagram (1:1000,000) of Shanghai city and its adjacent areas, which is 1990 and is provided by Shanghai Seismological Bureau) and bedrock geological map of Shanghai city(See Annex 3).

II. THE QUANTITATIVE EXPRESSION OF “HU-XI FAULT” IN THE DISTRIBUTION MAP OF MODIS SURFACE REFLECTIVITY

“Hu-Xi fault” is clearly quantitative expression in the fifth wave band of the distribution map of MODIS surface reflectivity.

A. The difference of reflectivity between “Hu-Xi fault” and the background a) The difference of reflectivity between “Hu-Xi

fault” and the background, in the distribution map of surface reflectivity generated by the fifth wave band of MODIS, is shown as Table

TABLE 1 THE REFLECTIVITY OF “HU-XI FAULT” IN THE FIFTHE WAVE BAND OF MODIS

position the surface reflectance Northwest Inside of

Fault Southeast

The maximum 0.267 0.2 0.294 The minimum 0.147 0.145 0.126 The mean 0.225 0.163 0.234 The average contrast of surface reflectivity 30%

B. The typical section plane characteristic of surface reflectivity of “Hu-Xi fault”

In the fifth wave band of MODIS distribution map of surface reflectivity, three reflectivity section plane vertical “Hu-Xi fault” is drawn. The three section planes are respectively AB, EF, CD (Figure 2).

1) The surface reflectivity section plane AB

The surface reflectivity section plane AB is nearby Wusong. The coordinate of A is 121.420E and 31.450N, and the geographic coordinate of B is 121.520E and 31.380N. The section plane AB and “Hu-Xi fault” are crossed at A1 and B1. The surface reflectivity section plane AB is shown in Figure 4.

In the Figure 4, the mean value of surface reflectivity section plane AA1 is larger than 0.22; the value of surface reflectivity is sudden drop from 0.26 to 0.16 at the interface A1 of “fault section plane”; the mean value of surface reflectivity is smaller than 0.16 in the “fault section plane” from A1 to B1 and the minimum is 0.14; the value of surface reflectivity suddenly increases from 0.16 to 0.24 at the interface B1 of “fault section plane”; the mean value of surface reflectivity section plane BB1 is larger than 0.23.

According to the analysis of the changes of the surface reflectivity, there is an area with small value of surface reflectivity between background A and B. The mean value of the surface reflectivity in the area is much smaller than that of background. It means that it is an fault and the width is approximately 10km.

2) The surface reflectivity section plane EF

The surface reflectivity section plane EF is nearby Baoshan, and the cross with “Hu-Xi fault” are E1 and F1. The geographic coordinate of E is 121.160E, and 31.410N, and that of F is 121.450E and 31.170N.

In the Figure 5, the mean value of surface reflectivity section plane EE1 is larger than 0.25; the value of surface reflectivity is sudden drop from 0.26 to 0.20 at the interface E1 of “fault section plane”; the mean value of surface reflectivity is smaller than 0.20 in the “fault section plane” from E1 to F1 and the minimum is 0.19; the value of surface reflectivity suddenly increases from 0.20 to 0.26 at the interface F1 of “fault section plane”; the mean value of surface reflectivity section plane FF1 is larger than 0.23.

According to the analysis of the changes of the surface reflectivity, there is an area with small value of surface reflectivity between background E and F. The mean value of the surface reflectivity in the area is much smaller than that of background. It means that it is a fault and the width is approximately 8km.

3) The surface reflectivity section plane CD

The surface reflectivity section plane EF is nearby Jinshan, and the cross with “Hu-Xi fault” are C1 and D1. The geographic coordinate of C is 121.07E, and 31.36N, and that of D is 121.400E and 31.360N.

In the Figure 6, the mean value of surface reflectivity section plane CC1 is larger than 0.24; the value of surface

reflectivity is sudden drop from 0.26 to 0.155 at the interface C1 of “fault section plane”; the mean value of surface reflectivity is smaller than 0.18 in the “fault section plane” from C1 to D1 and the minimum is 0.14; the value of surface reflectivity suddenly increases from 0.18 to 0.24 at the interface F1 of “fault section plane”; the mean value of surface reflectivity section plane FF1 is larger than 0.24.

According to the analysis of the changes of the surface reflectivity, there is an area with small value of surface reflectivity between background C and D. The mean value of the surface reflectivity in the area is much smaller than that of background. It means that it is a fault and the width is approximately 12km.

Combination of the above analysis and as shown in Figure 1, “Hu-Xi fault”, in the fifth-band distribution map of MODIS surface reflectivity of Shanghai city, is a continuous and stable banded. The value of surface reflectivity of “Hu-Xi fault” is slower than that of the background.

III. GEOPHYSICAL CONFIRMED FOR “HU-XI FAULT” Institute of Geological Survey of Shanghai confirms that

the existence and location of “Hu-Xi fault” entirely consistent with the position described in Geological Bureau of Shanghai , ” Regional Geology of Shanghai”, and photos (According to the aeromagnetic data, only the scale is different ,that is the length is about 60km and the width is 2-3km ).

As shown in bedrock geological map of Shanghai, the distribution map of surface reflectivity of Shanghai expresses the information of Bedrock Geology. The location of “Hu-Xi fault” is that of the basement faults (See in Annex 3). In the fault zone is Paleozoic Cambrian and Ordovician, and in the outside of the fault zone is mainly Jurassic. The difference between “Hu-Xi fault” and the background shows that the characteristic of bedrock geology between inside and outside of “Hu-Xi fault”.

The data of Institute of Geological Survey of Shanghai and the drill data confirm that the “Hu-Xi fault” is existence, such as the tenth drill of “Langxia-Dachang fault” and the nineteenth drill of “North Xinjing fault” (As shown in Annex, there is a fracture zone with 40m thickness at -300m. ). The new construction activity diagram (1:1000,000) of Shanghai city and its adjacent areas is supported by the aeromagnetic data and is provided by Shanghai Seismological Bureau. The location of “Hu-Xi fault” is consistence with its shown.

As shown in bedrock geological map of Shanghai, the distribution map of surface reflectivity of Shanghai expresses the information of Bedrock Geology. The location of “Hu-Xi fault” is that of the basement faults (See in Annex 3). The boundary of “Hu-Xi fault” in the distribution map of surface reflectivity is consistence with the boundary of the North-Northeast strip in the bedrock geological map of Shanghai. “Hu-Xi fault” in the distribution map of surface reflectivity reflects the type of rock and the information of characteristic. The Lower Paleozoic Cambrian, Ordovician and Jurassic volcanic rocks cut by “Hu-Xi fault” obviously control the development of the basin made of Cretaceous and Paleogene. The fault affects the development and the Sedimentary environment of the Cap formation and the

Geological hydrological background. And the information transferring through Groundwater - porosity - water content - reflectivity - remote sensing information did not found from the surface. “Hu-Xi fault” underground hundreds meters is shown in the fifth wave band of the distribution map of MODIS surface reflectivity (“Hu-Xi fault” underground is a broken with rich groundwater, which inevitably affected the soil moisture on it and vegetation growing by capillary action. MODIS-5 is the near infrared band. It is sensitive to Soil moisture and vegetation growing. So it generated a band with low value of reflectivity in the distribution map of surface reflectivity). It may be the main mechanism of the remote sensing discovery of “Hu-Xi fault”.

The underground buried fault is shown in the new construction activity diagram (1:1000,000) of Shanghai city and its adjacent areas, which is supported by the aeromagnetic data and is provided by Shanghai Seismological Bureau, and also is shown in the fifth wave band of the distribution map of MODIS surface reflectivity. On the same distributing map of surface reflectivity, we can find the other spacious fault information.

IV. CONCLUSION （1) The size, shape and the spatial distribution is clearly,

intuitively and panoramic view shown in the distribution map of surface reflectivity of Shanghai city on October 8, 2006. The previous obtained the information of the underground buried structure (such as Langxia-Dachang fault shown in annxe) by the aeromagnetic data and the drill date. All the data directly or indirectly prove the existence of the “Hu-Xi fault”.

（2) MODIS image is medium and low spatial resolution and multi-band remote sensing data. At macro expressing the underground buried structure with regional tectonic setting, the distribution map of surface reflectivity generated by MODIS image has advantage compared to that generated by the other high resolution remote sensing.

（3) At reflecting the deep underground buried structure, the distribution map of surface reflectivity generated by MODIS image is more direct, objective and deep than MODIS image [1, 2]. It is affected by many factors, such as comprehensive factors of atmospheric and ground in Imaging process and messaging between underground buried structure an the geological background.

（4) The spectrum features of target objects and geological background determine that different band of the distribution map of MODIS surface reflectivity have difference in showing underground buried structure (The fifth wave band is the best in showing “Hu-Xi fault”).

（5) The finding of “Hu-Xi fault” by remote sensing illustrates that the high spectral remote sensing image has the potential in surveying the underground buried structure. The distribution map of the surface reflectivity of special band of high spectral remote sensing has methodological meaning at searching the underground buried structure and the Paleoenvironment.

（6) “Hu-Xi fault” is a big fault nearby the most densely populated and most economically developed large city. The discovery and the confirmation of “Hu-Xi fault” has significance of the in-depth understanding and knowledge of ancient geographical environment and geological structure in Shanghai, and the prevention and reduction of disaster, and the sustainable development of national economy.

（7) We need further exploration, discussion and work to know the scale, the nature and the mechanism of remote sensing of “Hu-Xi fault”.

（8) The interpretation of remote sensing and especial the form of underground geological structure is very immature. There is something unknown on “Hu-Xi fault”. We hope to have an Academic Argument (methodology and epistemology).

REFERENCES [1] Chen Shupeng. The Temporal Dimension of The Analysis. Remote

Sensing Remote Sensing, 1997, 1 (3) :161-171. [2] Qing-Xi Tong, eds. The Analysis of Chinese Typical Surface Features and

Its Spectrum Science Press of Beijing, 1990. [3] "Regional Geology of Shanghai" and Photos from Shanghai Geological

Survey Institution. [4] The New Construction Activity Diagram (1:1000,000) of Shanghai City

and Its Adjacent Areas.

Figure 4 The new construction activity diagram (1:1000,000) of Shanghai city

and its adjacent areas, which is 1990 and is provided by Shanghai Seismological Bureau

Figure 3 The location of the section plane of “Hu-Xi fault

Figure 2 The fifth wave band of the distribution map of surface reflectivity of Shanghai city and its adjacent areas on October 8, 2006

Figure 1 ETM false color composite image of Shanghai

Figure 6 The surface reflectivity of section plane EF

Figure 5 The surface reflectivity of section plane AB

Figure 7 The surface reflectivity of section plane CD

Annex I: No.1 hole of North Xinjing karst-the diagram of the section plane of Chemical Institute geological (According

to the Shanghai Geological Chi)

Annex II: The card of Langxia-Dachang faults (Provided by Shanghai Geological Survey Institute)

Annex III: Bedrock Geological Map of Shanghai City