FIGURES

Figure 1.Comparison of historically observed moment magnitudes in northern California with the empirical rupture area and length relations of Wells and Coppersmith [1994].

Figure 2. Location map showing segmentation of faults labeled by codes (e.g., H2) that appear in Table A-1. Segment ends shown as X ; Great Valley blind thrusts as dashed lines with ticks; areal sources by dashed polygons labeled near centers. Faults with slip rate >1 mm/yr shown with thickness proportionate to slip rate. Locations: GG, Golden Gate; HOL, Hollister; MTJ, Mendocino triple junction; SJB, San Juan Bautista.

Figure 3.1906 slip from analysis of triangulation by Thatcher and others [1997]. Lithic patterns indicate extent of hypothetical segments (A2 and A3) where independent rupture is assumed.

Figure 4. Cartoon shows hypothetical sequence of slip accumulation along the joint San Andreas, San Gregorio and Sargent fault system.

Figure 5.Segmentation of Calaveras and Hayward faults. Circles show M>2 recent seismicity 1989-95; stars, historic events M³5.7 [Ellsworth, 1990] by year and magnitude. Open squares, trench sites (CA, Camille Ave.; LC, Leyden Creek; MH, Masonic Home; MT, Montclair; TP, Tule Pond; WC, Welch Creek); closed squares, trilateration arrays (VA, Veras; HV, Grant Ranch in Halls Valley); triangle SF19, alinement array. Locations: AC; Agua Caliente Creek; BT, BART tunnel; CR, Calaveras Reservoir; DC, Dublin Canyon; ER, Ellworthy Ranch; MC, Mills College; SL, San Leandro.

Figure 6. Hayward fault, historic earthquakes. Cartoon showing assumed locking patches at depth. See text for further discussion and explanation. Abbreviations as in

Figure 7. Hypothetical slip accumulation along Northern Calaveras fault. See text for further discussion.

Figure 8. North Coast seismicity (upper map, USGS catalog, 1968-1985) and creep localities (lower map). Rectangular area near Geysers (near L08) has seismicity deleted. Creep localities and geodetic sites marked by large triangles for alinement arrays and by small triangles with vectors for USGS trilateration stations and velocity analysis of M. H. Murray (unpub. data, 1996). Velocity vectors (arrows) indicate net right-lateral from P (Poonkinney) to Covelo of 8.3 mm/yr (1985-1989). See Figure 2a for location map of segments: C5, C6, C7, C8, H4, H5, H6 and H7.

Figure 9. Great Valley thrust faults. Segments used in this study (GV01-GV14); heavy dashed lines indicate blind thrust tips buried at 7 km depth. Gray rectangles show downdip extent of these hypothetical ruptures. Segments of Wakabayashi and Smith [1994](labeled WS-1 to WS-17) based mainly on geomorphic interpretation of range front. Quaternary faults of Jennings [1992] shown as dark lines for youngest faults and narrower gray lines for oldest faults. Other lines: antiforms (dashes and pluses), major piercements (MDA, Mount Diablo; NIA, New Idria) and surficial thrusts (continuous ticks, on hanging wall) [Jennings, 1977; Phipps, 1992]. Along Sacramento Valley margin, fine black lines indicate interpreted subsurface ramps (arrow lines point up-dip), flats (T's) and subsurface thrust tips (2-tick dashes) of Unruh and others [1995b]. Historical earthquakes shown as stars attributed by magnitude and year of occurrence [Ellsworth, 1990].

Figure 10. Path across northern Great Basin and San Francisco Bay area for summation of long-term geologic slip vectors on active fault systems. Faults: SA, San Andreas; H, Hayward; C, Calaveras; GV, Great Valley thrusts; HL, Honey Lake; L, Likely; SV, Surprise Valley; BR, Black Rock; JM, Jackson Mountains. L-T TZ, Lassen-Tahoe tectonic zone. Stars, Holocene volcanic centers (MLV, Medicine Lake volcano). Triangles, VLBI sites (HTC, Hat Creek).

Figure 11. Slip vectors assumed for this study shown as solid arrows and solid lines.

Figure 12. San Andreas fault system. Historical earthquakes [stars annotated by year and magnitude; Ellsworth, 1990; 1836 earthquake, Toppozada and Borchardt, 1997]. Simplified plate boundary, short-dashed line. Perimeter for summing of earthquake moment for Figure 13 shown by long-dashed line. GG, Golden Gate; MTJ, Mendocino triple junction; PKF, Parkfield.

Figure 13. Moment Rate of Model vs Historical Earthquakes. Only 50-70% of main seismic cycle has occurred in the historical period.

TABLES

Table 1. Measured Magnitudes of Northern California Earthquakes Versus Empirically Derived Magnitudes.

Table 2. Slip Vector Summation, Northern Basin and Range Province.

Table 3. Sum of Moment Rates for NCEP Model of San Andreas Fault System and Northeastern California.

Table 4. Comparison of Seismic Moment Rates for San Andreas Fault System.

Table A-1. Database of Potential Sources for Earthquakes Larger Than M6 in Northern California (simplified).

Table A-2. Method Used to Establish Seismic Moment Magnitude Mw) and Effective Recurrence Time (te).