Presentation Title

Using electrical resistivity tomography to characterize the shallow subsurface at the White Point Landslide area

Start Date

November 2016

End Date

November 2016

Location

HUB 302-133

Type of Presentation

Poster

Abstract

In November 2011, the White Point Landslide swept away a 420-foot section of Paseo Del Mar, the primary access road linking the coastal cities of San Pedro and Rancho Palos Verdes. An analysis of slope stability indicated that presence of water and groundwater pressure were the main contributors to instability. In order to examine these factors, we imaged the electrical resistivity of the subsurface in the area of the landslide through the use of electrical resistivity tomography based on data that we generated in multiple geophysical surveys. Resistivity is a property that indicates the resistance of a particular material to the passage of electrical current. Water has a low resistivity and electric current will follow the path of least resistance and therefore relatively low resistivity areas may indicate the presence of water-saturated material. Our survey consisted of six total 115-meter long lines with 24 electrodes spaced 5 meters apart, half of which were carried out before a rainfall event. After inversion of the datasets, all the resulting 2D models show zones of high resistivity from the surface to a depth of about 8 meters. There appears to be another high resistivity zone present in all the profiles, which is not as well imaged due to the limited data coverage at greater depths. These areas of high resistivity may be important to our understanding of the influence of water on the landslide, however, more research will be conducted with more powerful equipment in order to better examine the landslide area.

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Nov 12th, 1:00 PM Nov 12th, 2:00 PM

Using electrical resistivity tomography to characterize the shallow subsurface at the White Point Landslide area

HUB 302-133

In November 2011, the White Point Landslide swept away a 420-foot section of Paseo Del Mar, the primary access road linking the coastal cities of San Pedro and Rancho Palos Verdes. An analysis of slope stability indicated that presence of water and groundwater pressure were the main contributors to instability. In order to examine these factors, we imaged the electrical resistivity of the subsurface in the area of the landslide through the use of electrical resistivity tomography based on data that we generated in multiple geophysical surveys. Resistivity is a property that indicates the resistance of a particular material to the passage of electrical current. Water has a low resistivity and electric current will follow the path of least resistance and therefore relatively low resistivity areas may indicate the presence of water-saturated material. Our survey consisted of six total 115-meter long lines with 24 electrodes spaced 5 meters apart, half of which were carried out before a rainfall event. After inversion of the datasets, all the resulting 2D models show zones of high resistivity from the surface to a depth of about 8 meters. There appears to be another high resistivity zone present in all the profiles, which is not as well imaged due to the limited data coverage at greater depths. These areas of high resistivity may be important to our understanding of the influence of water on the landslide, however, more research will be conducted with more powerful equipment in order to better examine the landslide area.