Refractions: Head Waves, Diving Waves, Refraction Tomography Velocity Diving Waves (exist vertical dv/dz>0) z

Head Waves vs Diving Waves Velocity Head Wave z Velocity Velocity Velocity Diving Waves (exist vertical dv/dz>0) Interference Head waves z z

Diving Waves, linear V(z) grad. and Triplications http://arnica.u-strasbg.fr/Sismique/osis.html#FR Diving Waves, linear V(z) grad. and Triplications Velocity x x Direct Wave Refraction Direct Wave Refraction z z t p = sin i(z)/v(z) = 1/vmax A simple velocity gradient produces a refraction that takes a circular path, having a hyperbolic sine (or Error Function) shape in the t-x plot. V(z)=v + kz o Velocity x 3 arrivals at dash x 3 arrivals at dash Direct Wave Head Wave Reflection Direct Wave z t Reflection Refraction p = sin i(z)/v(z) = 1/vmax http://arnica.u-strasbg.fr/Sismique/prog/couche.html

p = sin i(z)/v(z) = 1/vmax Limit of thin horizontal layers Slowness = inverse apparent Vx P = sinO1/v1 = sinO2/v2=sinO3/v3=1/v4 v1 v2 v3 v4

Diving Waves, linear V(z) grad. and Triplications http://arnica.u-strasbg.fr/Sismique/osis.html#FR Diving Waves, linear V(z) grad. and Triplications Velocity x x Direct Wave Refraction Direct Wave Refraction z z t p = sin i(z)/v(z) = 1/vmax A simple velocity gradient produces a refraction that takes a circular path, having a hyperbolic sine (or Error Function) shape in the t-x plot. V(z)=v + kz o Velocity x 3 arrivals at dash x 3 arrivals at dash Direct Wave Head Wave Reflection Direct Wave z t Reflection Refraction p = sin i(z)/v(z) = 1/vmax http://arnica.u-strasbg.fr/Sismique/prog/couche.html

Diving Waves, linear V(z) grad. and Triplications http://arnica.u-strasbg.fr/Sismique/osis.html#FR Diving Waves, linear V(z) grad. and Triplications Velocity x 3 arrivals at dash x 3 arrivals at dash Direct Wave d d Direct Wave Reflection z Reflection t Refraction Head Wave p = sin i(z)/v(z) = 1/vmax Direct Wave Reflection Refraction Synthetics 40 s 80 s 10 deg 40 deg T-dx10 s Reflection Direct Wave Refraction T-dx10 s 40 s 80 s 10 deg 40 deg Gulf California Data http://arnica.u-strasbg.fr/Sismique/prog/couche.html

T(x,z) for a linear V(z) grad. Identify with circular arc: Thus: Source-receiver offset: Linear velocity variation: Constancy of apparent horizontal wave-number:

T(x,z) for a linear V(z) grad. Time: One can solve for Plugging Eq.(1) and (3) into Eq.(2), we finally get: From Asymptote:

Layered Medium & Critical Angle CSG Model 3 km/s Sea floor Post-critical reflection ray Post-critical reflections Z (km) Time (s) 4.0 3.5 1.5 km/s 6 6 X (km) X (km)

Shadow Zones and Caustics http://arnica.u-strasbg.fr/Sismique/osis.html#FR Sahdow Zones: http://www.iris.edu/hq/programs/education_and_outreach/visualizations/tutorial http://www.youtube.com/watch?feature=endscreen&v=JZyYs0tSo4k&NR=1 Shadow Zones and Caustics Shadow Zone II: http://www.youtube.com/watch?v=v_1QcI3BWRk Velocity x F Shadow Zone Caustic:Phase change results, large Amplitude,ray area zero,surface weak focus, Discontinuity of traveletime slopes z z x t Shadow Zone: An area on Earth's surface where no direct seismic waves from a particular earthquake can be detected. http://arnica.u-strasbg.fr/Sismique/prog/couche.html http://earthquake.usgs.gov/learn/animations/animation.php?flash_title=Shadow+Zone+Flash+Animation&flash_file=shadowzone&flash_width=220&flash_height=300

Shadow Zones and Caustics http://arnica.u-strasbg.fr/Sismique/osis.html#FR Shadow Zones and Caustics Romaowicz Lecture 1 hour: http://earthquake.usgs.gov/learn/animations/animation.php?flash_title=Shadow+Zone+Flash+Animation&flash_file=shadowzone&flash_width=220&flash_height=300 Shadow Zone: An area on Earth's surface where no direct seismic waves from a particular earthquake can be detected. http://arnica.u-strasbg.fr/Sismique/prog/couche.html

Head Wave, Diving Wave, post-Crit. Reflections Head Waves: Horizontal layered medium Vx = Vrefrac. Slope dx/dt in data = Vrefract. More generally: Refraction tomography. Post Crit. Reflections: Strong Amplitude More generally: Refraction tomography. Phase Change 3. Diving Waves: Phase Changes, Triplication Strong Amplitudes, Interfer. Head Waves, Shadow Zones, Caustics http://www.nature.com/nature/journal/v427/n6974/full/nature02231.html

Refraction Tomography t1 = L11/v1 + L12/v2 + L13/v3 + ….+ L1n/vn t2 = L21/v1 + L22/v2 + L23/v3 + ….+ L2n/vn

Refraction Tomography http://www.youtube.com/watch?v=Hrto0nIP8nk&feature=related Cool=falling blobs Cool colors = +v Hot=rising blobs Hot colors = -v 670 km discontinuity Any planet with a radius over ~1500 km cannot conduct its internal heat away within the age of the universe, so it must convect viscously to release its heat, or it would melt and then convect as a fluid. http://www.youtube.com/watch?NR=1&v=ve7N25R2h4c&feature=endscreen

Bedrock Depths from the Wells 3D Marine: http://www.youtube.com/watch?v=YNkJqJ2VAkQ&feature=related Bedrock Depths from the Wells here! Humboldt County Lander County The bedrock is expected to be at depth of several hundred meters from ground surface 677m Buffalo Valley Mine Pershing County #124 680ft(200m) #125 320ft(97m) 3.36km 15

Buffalo Valley Buffalo Valley Mine Seismic Line Pershing County North central Nevada Buffalo Valley Mine Seismic Line Pershing County 16

Survey Site 17

Seismic Recording Unit 18

Seismic Source 19

Comparison of Tomographic and Seismic Image Tomographic Image 300 Z (m) m/s Seismic Refractor Image 300 2500 Z (m) X (m) Amplitude A B C 22

Interpretation of Tomogram and Seismic Refractors m/s 300 2500 Z (m) X (m) A B C #124 #125 320ft (97m) 680ft (200m) 900 ft (273m) 845ft (256m) 2000 m (ch48 of Line C) 150 m off from the end 23