ASSESMENT OF FAULT ACTIVITY a mineralogical perspective_Radwan
•Download as PPTX, PDF•
1 like•534 views
Recommended
Recommended
More Related Content
What's hot
What's hot (20)
Viewers also liked
Similar to ASSESMENT OF FAULT ACTIVITY a mineralogical perspective_Radwan
Similar to ASSESMENT OF FAULT ACTIVITY a mineralogical perspective_Radwan (20)
More from Omar Radwan
More from Omar Radwan (18)
Recently uploaded
Recently uploaded (20)
ASSESMENT OF FAULT ACTIVITY a mineralogical perspective_Radwan
- 1. Term Paper- (GEOL 502) ASSESMENT OF FAULT ACTIVITY a mineralogical perspective Omar Atef Radwan g201306050 1
- 2. OUTLINE • Part 1: Basics of Fault Activity Assessment o What? o Why? o How? • Part 2: EPR Dating of Faults o EPR o EPR Dating o EPR Dating of Faults • Part 3: Case Study- Eupchon Fault, South Korea 2
- 3. 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 3 Fossen, 2010
- 4. WHY? active fault movement may result in many geologic hazards o strong ground motion o surface faulting o Landslides and rockfalls o Liquefaction o Tsunamis To assess the probability future earthquakes o Failure of large dams may cause floods o Failure of nuclear installations would cause radiation exposure o 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 4 McCalpin, Nelson, 2009
- 7. EPR • a.k.a: ESR • spectroscopic method used to detect paramagnetic species. • EPR spectrum: identification of paramagnetic species, their concentration, molecular structure 7 Brustolon and Giamello, 2009
- 8. EPR DATING 8 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.
- 9. EPR DATING 9 Equivalent Dose Determination actual EPR part of the dating procedure Dose Rate Determination calculated from the analysis of the radioactive elements (mainly Th, U, and K) in the sample and its surroundings EPR age T = accumulatedpaleodose Gy radiationrate Gy year = equivalentdose [DE] averageannual dose rate[D] Grün, 2008
- 10. EPR DATING OF FAULTS 10 • Method 1 EPR 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 2 EPR age of minerals precipitated within fault zones since the time of faulting.
- 11. CASE STUDY Eupchon Fault, South Korea 11Lee and Yang, 2007
- 12. 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: osynthetic and antithetic faults ohanging-wall anticlines odrag folds oback thrusts oflat-ramp geometries oduplexes
- 13. CASE STUDY Eupchon Fault, South Korea 13Lee and Yang, 2007
- 14. CASE STUDY Eupchon Fault, South Korea 14Lee and Yang, 2007
- 15. 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. 15
- 16. 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). 16
- 17. 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/ 17
- 18. 18
Editor's Notes
- Basis for eprdating: Trapping of electrons and holes An insulating mineral has two energy levels, at which electrons may occur: The lower energy level (valence band) is separated from the higher energy level (conduction band) by a so-called forbidden zone. When a mineral is formed or reset, all electrons are in the ground state. Ionizing radiation emitted from radioactive elements (U, Th, and K) knocks off negatively charged electrons from atoms. The electrons are transferred to the conduction band and positively charged holes are left behind near the valence band. After a short time of diffusion most of the electrons recombine with the holes. Some electrons can be trapped by impurities (electron traps) in the crystal lattice. The trapped electrons and holes form so called paramagnetic centers, which can be detected by ESR. When a sample is formed, it contains no trapped electrons; consequently, the eprsignal intensity is zero. After its formation, the mineral is exposed to natural radiation leading to the trapping of electrons and holes. This process will continue until the sample is measured in the laboratory.
- Schematic representation of the different components of natural radiation relevant for dose rate calculations: The dose rate is calculated from: 1.the concentrations of radioactive elements in the sample and its surroundings (only the U and Th decay chains and the 40 K-decay are of relevance; a minor contribution comes from 87 Rb in the sediment) 2.a component of cosmic rays. There are three different ionizing rays, which are emitted from radioactive elements Gamma rays have an average range of 30 cm. Thus, in homogeneous sediments, the gamma dose rate can be calculated from the chemical analysis of the bulk sediment. However, if the sediment contains boulders or intercalation of layers with different radioactivity, the gamma dose rate should be measured in situ. Beta rays have average ranges of a few mm. In smaller samples, such as teeth or shells, the volume that has received external beta dosage cannot be removed. For dose rate calculations, the sediment in the immediate surroundings of the sample is analyzed for radioactive elements. Alpha rays have average ranges of a few tens of micrometers. Alpha particles are less efficient in producing eprintensity than beta and gamma rays. Therefore, an alpha efficiency, which is usually in the range of 0.13±0.02, has to be determined. Cosmic rays are high-energy particles and are attenuated once they penetrate the sedimentary layers. about 300μGy/yr at sea level and decreases with depth below ground, and is also dependent on altitude as well as on geographic latitude For practical purposes, the cosmic dose rate becomes negligible at a depth of about 20 m.