COMPARISON WITH OTHER SEVERE EARTHQUAKES IN SAME REGION. 447 
Snelling. — Hard shock. Nodamage. (Merced Herald, Oct. 24, 1868.) 
Visalia. — Shock felt by few persons. (The Delta, Oct. 28, 1868.) 
Nevada. — At Gold Hill and Carson, shock perceptible to people awake, and a few 
people awakened. (Territorial Enterprise, Oct. 22, 1868.) 
The shock was apparently not felt in Ukiah, Yreka, San Luis Obispo, Los Angeles, 
Reno, Virginia City, Alpine County, Yuba County, Trinity County, or Oregon. 
SUMMARY. 
A review of the facts above presented regarding the earthquake of 1868 makes the 
following summary statement possible: 
1. The earthquake of 1868, like that of 1906, was due to an earth-movement on a 
rupture plane or shear zone which was manifest at the surface as a fault-trace. 
_ 2, The fault on which the movement took place was quite distinct from the San 
Andreas fault. 7 
3. It parallels the latter at a distance of about 18.5 miles to the northeast. 
4. Likethe San Andreas fault, it is coincident with an old diastrophic line upon which 
similar movements have been recurrent in time past. 
5. The old diastrophic line is marked by a degraded fault-scarp, which bounds the 
valley of San Francisco Bay and Santa Clara Valley on the northeast. 
6. Along this line there are certain geomorphic features analogous to those which 
characterize the San Andreas Rift. 
7. The fault-trace of the fault of 1868 was much shorter than that of 1906, having 
~ a known length of only 20 miles. 
8. The amount of horizontal movement, if any, was much less than on the San 
Andreas fault in 1906, and its direction is unknown. 
9. The vertical movement appears from the accounts given to have been small also, 
and to have been manifest as a downthrow on the southwest or bay side, altho this is 
not satisfactorily established. 
10. The fault-trace was characterized for the most part by a crack which in places, 
particularly on the lower ground, was superficially gaping. Associated with this main 
crack there were auxiliary branching cracks; and on the alluvial bottom-lands about 
San Francisco Bay there were numerous secondary cracks which were usually not dis- 
criminated by the observers of that day from the fault-trace. 
11. In harmony with the shortness of the fault-trace and the small movement ap- 
parent along it, the area of destructive effect was much smaller than in the case of the 
earthquake of 1906. This was true also of the entire area embraced by the isoseismal 
II R. F. While the data are insufficient for plotting the isoseismals satisfactorily, it is 
nevertheless clear that these curves plotted as ellipses on the map of California would 
have had much shorter major axes than in the case of the isoscismals for the earthquake 
of 1906; while the minor axes in a northeast-southwest direction would not differ greatly 
for the two earthquakes. We have no authentic reports of the earthquake north of 
Chico nor south of Monterey, altho perceptible tremors probably did extend further 
south. On the other hand, in a direction normal to the fault-trace the earth-wave made 
itself felt as far as the State of Nevada. 
12. The intensity was X in the vicinity of the fault-trace at Haywards. 
13. In San Francisco the chief damage caused by the earthquake was, as in 1906, on 
the made land and along the margin of the old shore and marsh border. But little 
damage was sustained by structures on the rocky slopes. 
14. The foot of Market Street, San Francisco, is about midway between the San 
Andreas Rift and the fault-scarp upon which movement occurred in 1868. The city 
