1. Exercise.04 Receiver functions will be determined Receiver functions will be inverted Receiver functions and surface-wave dispersion will be inverted jointly

2. Joint Inversion

3. Rayleigh Wave Sensitivity

4. RFTN Partials RFTN

5. Postulated Advantages of Joint Inversion Receiver function depends upon travel time and fine detail of structure related to conversions Surface wave is smoothly affected by velocities So Advantages of one overcome deficiencies of the other

6. Purpose of models Assist location by correctly predicting first arrivals Properly characterize dynamic wavefield to obtain quantitative estimates of source mechanism and strength

7. Receiver Function Sensitivity to Structure Perturb simple crust/mantle model Examine effect of gradient Design model to have same vertical travel time

8. Red = sharp / Blue = strong gradient

9. Gravity Anomaly Imagine sampling different structures within a region What would be seen in Bouguer anomaly

10. 180 mGal variation among models

11. Love Rayleigh

12. Surface waves Subtle differences in dispersion for fundamental mode in 20-30 second period range For surface waves to really contribute structure information, need dispersion for a fine grid of periods Need short periods to focus on upper crust

13. Receiver Functions Slides for different filter parameter - alpha =1.0 corresponds to a lowpass corner of about 1/3.14 Hz Focus on effect of Moho transition on nature of P-wave receiver function

19. Comments 1st peak controlled by shallow structure Gradient indicated by absence of signal for high alpha, character by low alpha Sharp moho is indicated by distinct bounce arrivals for all alpha, especially higher Simultaneous fit to several alpha robust

20. New Dispersion Data Harvard group velocities Colorado group velocities Phase velocities from Korea –Treat BB network as array –Optionally apply match filter –Apply McMechan and Yedlin p-tau implemented as sacpom96

22. 01 Jan 2001 Alaska Event - phase match output used from 10 stations

23. Blue - Colorado Green - Harvard Orange - Stevens Red - Korea phase velocity

24. Receiver functions Two filter parameters Stacked RFTN’s Arranged by similarity in shape Last 3 are from island stations Similarity in RFTN’s - > similarity in structure

25. Starting Model AK135 - depths > 50 km Upper 50 km is a halfspace with velocity of z=50 km Invert new dispersion Use stacked RFTN’s Use same script

28. Exercise cd Exercise.04 This used pre-existing SAC files. We must worry about the different byte order if the files were created on a SPARC or MAC and then analyzed on a PC. Solution saccvt -I tmp ; mv tmp f.sac

29. Step 2: rotate to great circle and then pick P more complicated under sac2000 than gsac

30. sac2000 Read three components synchronize for different start, end times save set cut reread save read horizontals rotate read 3 components - pick P

31. gsac Read 3 components rotate 3 components to great circle pick P save The script DOPREP automates this

32. Computation RFTN Use Ligorria and Ammon iterative decon The script DORFTN accomplished this. It also uses the epicentral distance and source depth to get the ray parameter RFTN computed for ALPHA = 0.5 1.0 and 2.5 Radial and transverse RFTN’s are saved.

33. Inversion tests Directories JOINT.0.5 has script for joint inversion using only the ALPHA=0.5 RFTN Directory JOINT.ALL will use all three ALPHA values. The RFTN.0.5 inverts only the RFTN. The purpose of these tests is to get a sense of the sensitivity of the inversion results to the particular data set used.

34. DOIT.deep Sets smoothing parameters Sets weighting, e.g., do not permit lower part of model to depart from global models of upper mantle Perform iterative inversion

35. RFTN

36. Joint

37. All models