Term Paper- (GEOL 502)

ASSESMENT OF FAULT ACTIVITY a mineralogical perspective

Omar Atef Radwang201306050

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OUTLINE

• Part 1: Basics of Fault Activity AssessmentoWhat?oWhy?o How?

• Part 2: EPR Dating of Faultso EPRo EPR Datingo EPR Dating of Faults

• Part 3: Case Study- Eupchon Fault, South Korea

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WHAT?

Earthquake is a term used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip, or by volcanic or magmatic activity, or other sudden stress changes in the earth. USGS -Earthquake Glossary

Active Fault: A fault that is likely to have another earthquake sometime in the future. USGS -Earthquake Glossary

Fossen, 2010

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WHY? active fault movement may result in many

geologic hazards o strong ground motion o surface faulting o Landslides and rockfalls o Liquefactiono Tsunamis

To assess the probability future earthquakeso Failure of large dams may cause floodso Failure of nuclear installations would

cause radiation exposureo Failure of chemical or petrochemical

facilities would induce fire, poisoning and environmental pollution among others.

in 1999 in Turkey 17,118 dead

in 2001 in India 20,023 dead

in 2003 in Iran 31,000 dead

in 2004 in Indonesia 250,000 dead

in 2005 in Pakistan 80,361 dead

in 2008 in China 69,000 dead

McCalpin, Nelson, 2009

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HOW?

Gradstein, 2012

6Gradstein, 2012

HOW?

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EPR

• a.k.a: ESR• spectroscopic method used to detect paramagnetic species.

• EPR spectrum: identification of paramagnetic species, their concentration, molecular structure

Brustolon and Giamello, 2009

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EPR DATING

Grün, 2008

oIonizing radiation produces paramagnetic centers with long lifetimes in a number of materials.

oThe concentration of these centers in a given sample is a measure of the total radiation dose to which the sample was exposed.

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EPR DATING

Equivalent Dose Determinationactual EPR part of the dating procedure

Dose Rate Determinationcalculated from the analysis of the radioactive elements (mainly Th, U, and K) in the sample and its surroundings

EPR age ሺTሻ= accumulated paleodose ሺGyሻ radiation rate ቀGyyearቁ = equivalent dose [DE] average annual dose rate [D]

Grün, 2008

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EPR DATING OF FAULTS

• Method 1EPR age of mineral grains that were crushed during comminution of the rock at the time of faulting. This method is based on the resetting of EPR signals, thus the subsequent radiation exposure produces new signals.

• Method 2EPR age of minerals precipitated within fault zones since the time of faulting.

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CASE STUDY Eupchon Fault, South Korea

Lee and Yang, 2007

12Kim et al., 2004

CASE STUDY Eupchon Fault, South Korea

The fault system includes one main reverse fault (N20°E/40°SE) with approximately 4 m displacement, and a series of branch faults, cutting unconsolidated Quaternary sediments.

Structures in the fault system include:o synthetic and antithetic faultso hanging-wall anticlines o drag folds o back thrustso flat-ramp geometries o duplexes

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CASE STUDY Eupchon Fault, South Korea

Lee and Yang, 2007

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CASE STUDY Eupchon Fault, South Korea

Lee and Yang, 2007

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CASE STUDY Eupchon Fault, South Korea

Results:• EPR ages from the Eupchon fault zone range from 2000 to 500ka. • The fault rocks were reactivated at least five times 2000, 1300, 900–

1100, 700–800, and 500–600ka ago. • potentially active fault • potential seismic hazards to the nuclear power plant in its vicinity.

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CONCLUSIONS

• Dating of prehistoric fault movements is a critical tool in the evaluation of geological hazards.

• EPR-dating is based on the direct measurement of the amount of radiation-induced paramagnetic electrons trapped in crystal defects. These ‘free’ electrons were generated by alpha-, beta- and gamma-radiation of natural radioelements (e.g. U, Th, K) and have accumulated in the minerals over geologic time.

• The EPR-age is obtained by dividing the total amount of accumulated radiation dose by the dose per year (annual dose).

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REFERENCES• Brustolon, M., Giamello, E., 2009. Electron Paramagnetic Resonance: A Practitioners

Toolkit, 1 edition. ed. Wiley. 539p.• Fossen, H., 2010. Structural geology. Cambridge University Press, Cambridge; New

York.• Gradstein, F.M., 2012. The geologic time scale 2012. Elsevier, Amsterdam; Boston.• Grün, R., 2008. Electron Spin Resonance Dating, in: Pearsall, D.M. (Ed.), Encyclopedia

of Archaeology. Academic Press, New York, pp. 1120–1128.• Kim, Y.-S., Park, J.Y., Kim, J.H., Shin, H.C., Sanderson, D.J., 2004. Thrust geometries in

unconsolidated Quaternary sediments and evolution of the Eupchon Fault, southeast Korea. Island Arc 13, 403–415.

• Lee, H.-K., Yang, J.-S., 2007. ESR dating of the Eupchon fault, South Korea. Quaternary Geochronology, LED 2005 11th International Conference on Luminescence and Electron Spin Resonance Dating 2, 392–397.

• McCalpin, J.P., Nelson, A.R., 2009. Chapter 1 Introduction to Paleoseismology, in: James P. McCalpin (Ed.), International Geophysics, Paleoseismology. Academic Press, pp. 1–27.

• USGS -Earthquake Glossary: http://earthquake.usgs.gov/learn/glossary/

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