Illustrations

1. Geologic and tectonic index map of Northern Cascadia

2. Gravity and magnetic maps of Washington State

3. Magnetotelluric models for profiles AA', BB', and CC'

4. Earthquakes with magnitudes greater than M4.0 in northern Cascadia

5. Grid used for western Washington tomographic velocity model

6. Grid outlines for regional Washington velocity model and detailed Mt. Rainier model

7. Vertical cross-sections of P-wave velocities along east-west transects

8. Vertical cross-sections of P-wave velocities along north-south transects

9. Isosurface of P-wave velocities for value of 7.5 km/s

10. Overhead view of 7.5 kn/s isosurface

11. Isosurface of P-wave velocities from regional model at 7.0 km/s

12. Multiple vertical-slice plot for western Washington with basins and SWCC

13. Map of elevations of base of Quaternary in Seattle Basin

14. Row 14 model velocity section

15. Detailed view of pluton near Mt. Rainier from velocity model

16-30. Row 16-34 velocity model sections

31-42 Column 10-42 velocity sections

43. Vp/Vs results from tomographic P and S-wave velocity models

44a. Interpretive geological cross-sections

44b. Interpretive geological cross-sections

45. Selected focal mechanisms from Cascadia

46. Summary of all recorded earthquakes in Washington, 1970-1997

47. Earthquakes at depths of 0-10 km

48. Earthquakes at depths of 10-20 km

49. Earthquakes at depths of 20-30 km

50. Earthquakes at depths of 30-60 km

51. East-west seismicity cross-section

52. North-south seismicity cross-sections

53. Stress and deformation indicators

54. Finite-element grid used in anelastic models for Cascadia

55. Heat flow values for Cascadia

56. Maximum horizontal stress vectors from best-fitting Cascadia model

57. Stress vectors for low subduction thrust tractions

58. Plate interactions in western North America

59. Pn anisotropy results for Cascadia

60. Finite-element stress model of western U.S.

61. Surface velocities for best-fitting Cascadia model

62. Fault slip rates for best-fitting Cascadia model

63. Earthquakes at depths of 15-30 km in relation to key Crescent Formation block

64. Radiocarbon date evidence for 1100 yr B.P. earthquake in Puget Sound region

A1-Resolution tests for P-wave velocity model

CONTENTS