Hi All. When Mr. Bettis went to work on the morning of Tuesday, April 19, 1892 little did he know that it was going to be a morning unlike any other he ever had.

He was walking down Main Street at 2:50 a.m., lantern in hand, when "his attention was attracted by a rumbling sound coming from the hills west of town. The noise resembled distant thunder or the roaring of water which had suddenly been let loose by the bursting of huge dam gates. Bettis stood still and listened a few seconds, while the noise increased to a roar and the ground beneath his feet seemed to heave up. 'I felt as if I was on the deck of a vessel during a heavy storm, and I put my hands to the ground to prevent myself from falling on my face. After that brick walls and chimneys began to fall all around and the noise for a minute or so was deafening' “ This was the M>6.5 est. Vacaville quake.

S. B. Dunton of Winters was on the cement grade when the 9:45AM shock came [April 21, 1892], . . . I had just cleared the road of rocks up to the county line, some of which weighed 2,000 lbs.; I rolled them with my team and chain. Rocks of 50 tons came down the mountain a distance of 500 or a 1,000 feet, crashed through pines, over the road and into the creek, to join many other like boulders, that had proceeded them many centuries before from like causes. One of those "needle points" south side of canyon above the "Black Rocks" broke off. There are many slides and immense boulders toppled over, and they came into the creek with a tremendous crash. The upper canyons and Berryessa Valley were not shaken so hard. The focal point of greatest force was on the Black Rock line and Vacaville (is) directly in the path of this lava line of fracture and ancient volcanic ebullition.

The "cement grade" corresponds to the present State Highway 128 that traverses Putah Canyon west of Winters and the "Black Rocks" are identified on the map by Kirby and Crook (1934). These "Black Rocks" refer to several small exposures of basalt located immediately north of the previously mentioned location in Putah Canyon where the Creek makes a bend to the southeast (base of the Tehama Formation). The "Black Rock line" and "lava line of fracture and ancient volcanic ebullition" described by Dunton evidently corresponds to these small remnants of basalt (Putnam Peak Basalt). Use of the word "above" in the phrase . . ."those 'needle points' south side of canyon above the Black Rocks . . ." undoubtedly means "farther up" the canyon. Very large boulders and some rock spires exist along one of the two north-south-trending ridges that intersect the canyon about a mile west of the "Black Rocks." This was the M>6.2 est. Winters quake.

The thing that has puzzled seismologist was which fault, or faults did these quakes occur on. Did they even occur on a fault?

(1) The Midland fault, or an unidentified (concealed) fault along the western valley margin.

(2) A fault in the English Hills or Vaca Mountains such as,

an unidentified (concealed) fault in Vaca Valley-Pleasants Valley, the possible northern extension of either the Vaca fault or faults treading northerly from Lagoon Valley or, an unrecognized bedding plane fault associated with the steeply dipping Great Valley sequence.

(3) The active Green Valley fault or another fault west of the crest of the Vaca Mountains.

(4) Rupture resulting from active folding, with no clear association with any fault having surface expression, as was the case in Coalinga in 1983.

No quakes of this magnitude (M>6.5) are known to have occurred in the area prior to these quakes. However this isn’t very reassuring that no quakes of this magnitude have ever centered there.

The only known M >5.0+ earthquake to occur in the area was an event of about M 5.5 on May 19, 1902. From the available intensity data, this event was located in the Fairfield-Vacaville (Solano County) area (Toppozada and others, 1981).

Between 1900 and 1974, only three events (in the M 4 range) were located within the study area (Real and others, 1978). These were located in the hills east of Blue Ridge between Putah and Cache creeks. The accuracy of the epicenter locations is uncertain. More recently an M 4.2 earthquake occurred near Madison in Yolo County (September 8, 1978).

Now comes the question. Can they happen again? I think the answer to that is yes. However this time the devastation will be much greater due to the population density. Take Care…Don in creepy town

Reference:

JOHN H. BENNETT

Division of Mines and Geology, April 1987

• Vacaville/Winters Quakes