THE EARTHQUAKE AS A NATURAL PHENOMENON. 
fault trace and diminished with distance therefrom ; but to this rule 
there are important exceptions, and it has been noted especially 
124° 123° 
122° 
41° 
1 \ 1 
-300 miles / 
.^Eureka, 
1/ FeiVdale 
Cape \) \^ 
Mendocino JS ^^"\ 
l o U 
UPetrolia ^5^ 
1 ) 
4-1° 
V S^ 
/ ^ 
-250 K\ 1, 
40 
N \ X 
— \Pt.Delgada\ ^> 
40° 
N !V \ 
\ * 
N in \ 
v 
-2O0 \ \0> / V. 
X \\ 
\\ ° r\ 
\]* 
;v;i 
Point Arena \\-<\ ^-^} 
-150 W^ ^vT*'" 
\ ° 
v \ Santa 
c 
39 
Sacramento V 
Rosa ) 
^ TomalesBacy\^ 
-100 rs hwerness/^k 
26 
p J *Sa.n> ^X ~" 
38 
Bolinas^N^ 
^ vOBerkeley "=> \ 
-|& VOakland "* V 
SAN FRANCISCO^ 
Mussel Rook 
o 
\ \%- 
-SO 
j V r- San Jose 
1 \v> 
o 
V v 
37 
-o ^l^- 
Santa Cruz \ \ HolHster 
\ X ° 
/ San Juan 
37* 
1 1 
X"Monlerery 
1 \ 
124° IZ3° 
122° 
Fig. 1. — Map of the fault trace. Broken lines indicate alternative hypotheses as to its 
extension north of Point Arena. 
that an area of high intensity coincided approximately with the 
Santa Rosa Valley, which trends northwestward, parallel to the main 
