1. Environmental and Exploration Geophysics II tom.h.wilson wilson@geo.wvu.edu Department of Geology and Geography West Virginia University Morgantown, WV Intro Lecture (Fall 05) Wave Types and Travel Paths - Example Applications

2. Environmental and Exploration Geophysics II Course Syllabus Prerequisites Grading Exploration Project Term Report Computer Software/ Computer Labs

3. Grading 30% on computer labs, 30% problem sets, 10% mid term exam, 15% term report/project and class presentation, 15% final exam.

4. Course Objectives I. Provide discussions of basic principles in reflection and refraction seismology and ground penetrating radar. II. Provide experience with the application of these principles to non-invasive investigations of subsurface conditions important to environmental assessment of hazardous waste sites and groundwater exploration, engineering studies, and resource exploration. Student choice of term project and term report help the student focus geophysical applications on their primary interest whether exploration or environmental assessment III. Provide an introduction to computer modeling as a problem solving tool. IV. Develop oral-presentation and report-writing skills.

5. Do you have any general questions about the format of the course, course content, grading … etc?

11. The 8 bit recording range corresponds to a -128 to 127 range of integer values – no decimals!

12. So - to see additional detail in the ground motion - to measure the fractional motion - you need to increase the dynamic range of the recording system. The engineering seismograph we demonstrated in class today is restricted primarily to the shallower applications since events that have traveled great distances will have very small amplitude (less than 1on the scale of ±128). Dynamic range refers to the number of bits available to store information An 8 bit (1 byte) record allows one to store numbers in the range -128 to 127 A 32 bit record allows one to store numbers in the range -2,147,483,648 to 2,147,483,647.

13. Liner and Liner, 1995 Processed GPR profile

14. Miller et al. 1997 Seismic and GPR methods both record waves that have been reflected from subsurface interfaces. In the one case (GPR) these waves are electromagnetic (and much faster), in the other (Seismic) they are acoustic or mechanical waves.

16. Body Waves

17. Surface Waves

19. In general V R <V L <V S <V P But this is not strictly true. The Love wave is a surface wave and its velocity will be equal to the shear wave velocity in the upper medium. The Love wave like the Rayleigh wave is also a dispersive wave. That means that deeper Love wave motion usually propagates more rapidly since velocity increases with depth. Shear waves beneath the surface layers are generally much faster than those in the surface, so in application, the shear waves that we are concerned with generally have higher velocity than the Love waves.

20. Love waves tend not to be recorded in the conventional seismic survey where the interest is primarily in the recording of P-waves. The geophones used in such surveys respond to vertical ground motion and thus do not respond to the side-to-side vibrations produced by Love waves. Rayleigh waves produce large vertical displacements and are a significant source of “noise” in the conventional P-wave reflection seismic survey.

28. Wave Packet

32. How do waves move from one place to another?