from
VACAVILLE-WINTERS EARTHQUAKES . .
.1892
Solano and
By
JOHN H. BENNETT
Division of Mines and Geology
INTRODUCTION
This article is based on research of newspaper and other accounts of
pre-1900 earthquakes in
Vacaville's night watchman, S. N. Bettis, 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' " (Perrine, 1893, p. 20).
On that Tuesday morning,
The larger
Intensity VIII and greater effects were felt as far north as the
communities of Esparto and Capay in
PREVIOUS WORK
No causative fault has been identified as the source of the 1892
earthquake sequence. Past speculation generally focused on the
Newspaper accounts of the 1892 earthquakes were compiled from some 40
periodicals and other reports "with particular emphasis on establishing
the location of the epicenters" (Dale, 1977). From this study it was
concluded that "the epicentral region for the major events of the April
19-29, 1892, series of seismic events . . .was not in the Central Valley, as
had been previously assumed, but rather in the hills bordering the valley west
of Vacaville and Winters" (Dale, 1977).
FIGURE 1
Figure 1. Faults in the Vacaville-Winters region. After Wagner and
others, 1981, and Wagner and Bortugno, 1982, except as noted on map.
An exhaustive search of reports of all pre-1900 California earthquakes,
including the examination of nearly 12,000 newspaper issues, mission records,
diaries, and other accounts was completed in 1981 (Toppozada and others). From
these data, isoseismal maps were developed for all significant pre-1900 events
and, whenever possible, magnitudes and epicentral locations were estimated. The
resulting isoseismal map for the larger event of the April 1892
Vacaville-Winters sequence (Figure 2) was developed from intensity data derived
from a search of some 65 newspapers published throughout northern California
and western Nevada. The following conclusions were determined from these data
(Toppozada and others, 1981).
Earthquake of April 19, 1892 - Estimated M 6.4
Extensive damage (VIII MM) occurred at Dixon and Vacaville, Solano
County and at Winters, Yolo County. The highest intensity (IX MM) was assigned
to Allendale, between Vacaville and Winters. A number of buildings in the
vicinity of Allendale collapsed, were shifted off their foundations, or were
wrenched apart. Fissures extending about a mile were opened in the ground near
Allendale, which suggests possible faulting (The Dixon Tribune, 29 April 1892,
p. 2). The area shaken at intensity VIII MM or greater was about 1,100 km2.
Earthquake of April 21, 1892 - Estimated M 6.2
Considerable damage was done to weakened structures in those communities
damaged by the 19 April event. The area shaken at intensity VIII MM or greater
was about 890 km2, but this area was probably larger than normal due to the
weakening of structures during the earthquake on the 19th.
Earthquake of April 29, 1892 - Estimated M 5.5
This was an aftershock of the 19 April earthquake. The highest assigned
intensity (VI MM) was at Davisville (Davis), Yolo County where a few loose
bricks fell and at Sacramento where many people ran out.
INTENSITY DATA
The following general observations are based on the intensity data:
(a) The intensity pattern is asymmetrical with contrasting very high and
relatively low intensities occurring on opposite sides of a line near and
parallel to the Napa-Solano county line (Figure 2). There are, in fact, no
intensities greater than VI (MM) at any of numerous locations within Napa
County including Napa, Rutherford, St Helena, and Calistoga in Napa valley;
Pope Valley, midway between the upper Napa Valley and Lake Berryessa; nor at
the former community of Monticello in Berryessa Valley (now inundated by Lake
Berryessa) where damage was "nominal." Consistent with these low
intensities in Napa County are the reported effects from Mare Island and
Cordelia in Solano County (V-VI MM). The intensity data indicate that the
source area was east of the crest of the Vaca Mountains.
(b) Various newspaper reports of the April 19 event indicated that
"Vacaville seemed to be the center of the disturbance (Western Watchman,
April 23, 1892, published in San Francisco). These reports were probably based
upon the fact that there was more, but not necessarily more severe, structural
damage at Vacaville. As pointed out by Dale (1977), the extent of damage in
Vacaville may have been due more to unfavorable foundation conditions than
proximity to the epicenter. An article in the Sacramento Bee, dated April 20,
1892, noted that, "Eulatis Creek runs through the town of Vacaville. It
was noticed that most of the damage was on the south side. This was mainly
because nearly all the buildings are in that direction, but it is stated that the
shock was not as severe on the north side of the creek . . . The difference in
the violence of the shock is explained by the character of the soil, which is
not so deep on the north side of the creek, affording a solid foundation."
Most of the downtown area south and west of the creek is on alluvium, while
sandstone is common to the north and east.
(c) Accounts of the April 19 event in the Winters-Pleasants Valley area
describe numerous cracks and fissures, sounds of escaping gas, water thrown
from creeks and rockslides. Similar reports of manifestations of high-intensity
shaking are generally lacking elsewhere.
(d) The analysis of the intensity data for the April 19 event resulted
in assigning maximum intensity (IX MM) to the area near Allendale, about midway
between Vacaville and Winters (Toppozada and others, 1981).
(e) The April 21 event is reported as follows: "It is quite clear
that the focus of today's disturbance has been shifted to the northwest and has
been located near Winters. Elmira and Vacaville got off lightly. The direction
of the shocks has also perceptibly changed" (Morning Call, April 22, 1892,
published in San Francisco).
Earthquakes of this magnitude could involve fault rupture exceeding the
20 km distance between Vacaville and Winters and generally equivalent damage at
these locations is reasonable assuming rupture along some intermediate fault.
The various damage accounts, taken collectively, suggest that the source of
both events was located somewhere between these two communities. There is no
compelling evidence to conclude that the two events were widely separated
spatially, though various reports indicate that the April 21 event was the more
northerly of the two.
HISTORICAL SEISMICITY
Historical seismicity is nominal and provides no insight to seismically
active areas within the study area. Other than the 1892 earthquake sequence,
the only known M > 5 earthquake to occur in the area was an event of about M
5½ 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 these
epicentral locations is uncertain. More recently a M 4.2 earthquake occurred
near Madison in Yolo County (September 8, 1978).
FIGURE 2
Figure 2 Modified Mercalli isoseismal map of the April 19,1892 Vacaville-Winters
earthquake, (10:50 GMT) Modified from Toppozada and others, 1981.
Precisely located hypocenters and focal mechanisms in the eastern San
Francisco Bay region for the period 1969-1980 were examined (Ellsworth and
others, 1982). These data reveal a broad north-south trending zone of
seismicity along the western margin of the Montezuma Hills north of Pittsburg
(Contra Costa County). Focal depths are unusually deep, plunging north to a
depth of 25 km. Focal mechanisms are consistent with right-lateral strike slip
motion parallel to the seismicity. The area involved is located astride the
Vaca-Kirby Hill fault (Wagner and others, 1981) (Figure 1). More recently the
regional seismicity was summarized and it was noted that recent earthquake
clusters north of Antioch, and in the vicinity of Williams, and at Butte City
define a seismic zone along the western margin of the Sacramento Valley that
could represent the source of the 1892 events (Eaton, 1986).
POSSIBLE CAUSATIVE FAULTS
From an initial overview of the many newspaper accounts and isoseismal
maps (Toppozada and others, 1981) the general area for the source of the 1892
earthquake sequence was determined (Figure 1). There are several known or
suspected faults within the area that either have been or could be regarded as
the source of this earthquake sequence. These include the following:
(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,
(a) 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,
(b) 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.
The Midland Fault
The Midland fault was evaluated in connection with the Alquist-Priolo
fault-zoning program, as follows (Bryant, 1982):
The Midland fault zone is thought to be a north-northwest trending,
steeply west-dipping normal fault. The fault zone depicted by Jennings (1975)
connects with the Sweitzer fault, an east-dipping reverse fault exposed in the
Rumsey Hills (Kirby, 1943) (Figure 1). However, Wagner and others (1981) did not
find evidence supporting the connection of the Midland fault with the Sweitzer
fault. Indeed evidence supporting the existence of the Midland fault north of
Winters was not found (Wagner, personal communication, 1982).
No observed evidence of displacement on the Midland fault younger than
early Oligocene time was reported by Reynolds and Reynolds (1963). Another
study did not show beds younger than early Tertiary as offset by the Midland
fault (Wagner and others, 1981). However, most of the data on the Midland fault
has originated from oil and gas exploration. Thus, it should be recognized that
data on non-petroleum bearing formations may not have been as carefully
developed and interpreted, possibly overlooking the offset of upper Tertiary
formations. The Midland fault has not been mapped as an observable surface
feature by any worker, including Sims and others (1973), Helley and Herd
(1977), and Helley and Barker (1979).
Fault Along the Valley Margin
A major fault along the valley margin was postulated by Thomasson and
others (1960, p. 40):
North of Winters, the east margin of the foothills is remarkably
straight and abrupt. The dip of one exposed gravel bed steepens at the margin
of the hills, and the dips of the underlying fine-grained strata appear to
steepen also. This marginal steepening becomes accentuated going north,
indicating either a monocline whose degree of flexure increases to the north,
or a hinge fault whose displacement increases northward, or possibly both.
Bryan (1923) has, in fact, postulated a fault along the margin of the hills
between Putah and Cache creeks.
An authoritative description of this fault was presented in a geologic
report of the Sacramento Valley as follows (Bryan, 1923, p. 79-80):
Another fault . . . starts at Esparto and skirting the mountains, brings
up the alluvium along the foothills to a point opposite Allendale, where the
fault disappears." and (on p. 224), ". . a . . . fault, with uplift
on the west side. It begins near Esparto, skirts the mountains along the low
bench already referred to, crosses Putah Creek east of Winters, and dies out
near Allentown (Allendale).
A fault in this same location was depicted by Willis (1923) as lying
between Esparto-Capay and Winters.
Several newspaper accounts describe effects of the 1892 earthquake that
could be interpreted as expressions of surface rupture associated with a fault
along the valley margin:
(1) At the northern extremity of this postulated fault near
Esparto-Capay the San Francisco Examiner (April 20, 1892) reported, "The
earth opened in several places between here (Esparto) and Capay."
(2) In the immediate vicinity of Winters there are several reports of
ground failure. Whereas all of these are probably related to secondary failures
along Putah Creek, some could be interpreted as manifestations of surface
rupture.
(a) It must have been a fearful shock. The sand bars in Putah Creek (to
the west and south of Winters) opened, and from the fissures the water spurted
high upon the banks . . . In some places the creek became a dry, in others it
changed to a torrent. The banks caved-in in some places and almost dammed the
stream (San Francisco Examiner, April 22, 1892).
b) Near the town the bank of Putah Creek, ten feet wide, caved in, and
along the bottom of the creek for a great distance rents were made by the
shocks (San Francisco Chronicle, April 20, 1892).
c) At Winters there have been developed a number of fissures in the
earth, water has been ejected, gas has escaped, and the bed of the creek has
been filled up for a distance of over 70 yards (Perrine, 1893, p. 31).
(d) The greatest damage done by the earthquake outside of that wrought
in the town itself is in the wrecking of the country road skirting Putah Creek,
on the south side of the town . . . A new road will have to be cut through
adjoining property, as a dangerous cliff fifty feet deep has been formed at the
spot where the embankment gave way. A long zigzag fissure six inches wide
extends right along the center of the roadway. As in nearly every other case
the fissure was north and south . . . (Morning Call, April 22, 1892, p. 2).
(e) On Putah Creek, half a mile west of Winters, a phenomenon was
witnessed by a young man named Fred Willis, who was riding past at the time of
the big shake. There seemed to be an explosion, and the water was thrown from
the creek to a distance of twenty feet on either bank. Then followed a hissing
sound as of gas escaping. At daylight several fissures were found in the bed of
the creek and in the roadway and fields adjoining. On each side of the creek
where the explosion took place the banks caved in, the landslides being
seventy-five feet in length and twelve feet deep (San Francisco Examiner, April
21, 1892, p. 1).
(3) Southeast of Winters, near Allendale, two newspaper reports describe
a fissure that is not ascribed to secondary ground failure or shaking effects:
(a) The San Francisco Examiner (April 23, 1892) reported this fissure as
follows:
A FISSURE HALF A MILE LONG --- It is also a fact that out by the old
Allendale road, five miles west of Dixon, a fissure in the ground can be traced
for fully half a mile. It opened at first over an inch wide and closed again as
the edges of the crack crumbled inwards. Now all that is left is a ridge of
fine dust, like the trail of some huge insect.
(b) The Dixon Tribune (April 29, 1892) reported:
The earthquake opened fissures in the earth near Allendale from one to
three inches in width and extending about a mile.
The trend and continuity of these cracks were not reported. Ground
cracking due to shaking was widespread throughout the area. The Morning Call
(April 22, 1892) indicated that most of the fissures observed throughout the
area had a general north-south trend. The cracks described near Allendale
appear to have been extensional rather than a mole track formed by
compressional deformation.
One can assume that the fissure near Allendale was noticed because of
its proximity to the Allendale Road. If it was surface rupture it may have been
of greater length than reported since the feature, as described, was relatively
obscure, and may have been intermittent and/or offset along a greater length.
Considering these factors and the rural setting, the full extent of a more
lengthy surface rupture could have gone unnoticed.
If a fault exists at this location, it could constitute the southerly
extension of a fault located along the linear valley margin between Winters and
Esparto-Capay (Willis, 1923; Bryan, 1923; and Thomasson and others, 1960).
It could be speculated that the earthquakes resulted from rupture that
involved a westerly dipping thrust fault, the 'fissure' evidencing rupture that
reached the surface only along this limited segment. Given this model the areas
of highest intensity (Allendale, Pleasants Valley, west of Winters) would be
situated on the hanging wall, a setting analogous to that at San Fernando in
the 1971 earthquake, where the area of greatest damage was similarly located
(Steinbrugge and others, 1975).
In the vicinity of the reported rupture several northwest-trending,
right-laterally deflected drainages and other associated lineaments were noted,
although no systematic magnitude of deflection or other evidence of recent or
recurrent surface faulting was evident (Bryant, 1982). During recent trenching
of one of the most pronounced lineaments by the University of California,
Davis, no evidence of faulting was found (Martha Merrian, 1986, personal
communication).
Faults in the English Hills/Vaca
Mountains
A fault within the English Hills was mapped by Thomasson and others
(1960) and also by Sims and others (1973). From its southern extremity, this
fault projects southeasterly across the English Hills along the approximate
base of the Tehama Formation. According to Thomasson (1960), "The location
of the southeastern end of this fault is not certainly known." Toward the
north, Sims and others (1973) show this fault extending from the English Hills
across Pleasants Valley to within about two miles of Putah Creek. This fault is
not regarded as an active feature by Sims and others (1973).
Two faults, which trend northerly across Cement Hill northeast of
Fairfield, possibly merge within Lagoon Valley and extend north to a point
about 2 miles west of Vacaville before terminating at the alluvium in Vaca
Valley near Alamo Creek, were mapped by Sims and others (1973). Continuation of
faulting northwesterly into Vaca Valley is a reasonable extrapolation.
Another fault that may extend into Vaca Valley is the Vaca fault (Wagner
and others, 1981). This fault, mapped by Bailey (1931), trends northwest along
the northeast flank of the hills just south of Vacaville terminating at the
alluvium at the southern end of Vaca Valley just west of Vacaville (Figure 1).
Wagner and others (1981) show the Vaca fault extending southerly across Travis
Air Force Base to connect with the Kirby Hills fault west of the Montezuma
Hills, A prominent zone of seismicity is associated with the trend south of the
Montezuma Hills, defining a zone that includes the Livermore earthquake
sequence of January 1980 (Eaton, 1986).
The Clark fault, named by Kirby and Crook (1934), was mapped by Sims and
others (1973) southerly from Capay Valley into the mountains east of Lake
Berryessa and Rocky Ridge. This fault is also inferred to extend north into
Capay Valley (Sims and others, 1973). Kirby and Crook (1934) speculated that
massive vertical sandstone beds located along Enos Creek several miles to the
south might be an expression of this same fault. This fault was also mapped
along the same south-southeasterly trend by Brooks (1962). Projection of this
fault south of Enos Creek intersects Putah Creek near the base of the Tehama
Formation where Putah Creek makes an abrupt change from an easterly to a
southeasterly course about 5 miles west of Winters.
EARTHQUAKE EFFECTS
English Hills/Vaca Mountains
The following letter describes the effects of the April 19, 1892
earthquake at the Cantelow Ranch in the English Hills. It was written by
Lawrence A. Cantelow to his parents in San Francisco on the day following this
event. The Cantelow Ranch was located about 1/2 mile southeast of Putnam Peak
(Figure 1). (This letter was provided by Herbert P. Cantelow, of Oakland and
nephew of the two Cantelow brothers, both of whom resided at the ranch in
1892.)
Cantelow Ranch
April 19, 1892
Dear Folks,
The chimney here broke off at the top of the house, but did not break
through the roof. All the back fell out and it is badly cracked around the
fireplace. There was about a ton of brick and dirt. In the sitting room the
tables and desk were thrown over and pictures turned wrong side to. In the
little room where I sleep, the shelves were all torn down and everything
generally tumbled over. In Nomia's room the bureau was turned over on its face,
pitcher and wash bowl broken, and the bed wheeled across the room. The big
clock is a total wreck---the frame is all peeled apart. In the dining room not
much damage was done as there was nothing in there.
But in the kitchen! You should have seen the mess---milk, jelly,
preserves, coal oil, sugar, flour, tea, in fact everything all in one mess and
this held down by four big wheelbarrow loads of dishes and bottles broken into
ten thousand pieces. It just naturally smashed everything in the room but the
stove. I think at one time the east end of the house was four feet from the
ground. The underframing is all knocked galley west and the two parts of the
house are split apart so there is a crack in the door big enough for a cat to
go through. The cap is knocked off the stovepipe.
. . . There is a big crack running across the lot and up the hill. I
don't know how long, as I did not go to the end of it, but it is so big that
the cows were afraid to cross it, and in two places where it crossed the fence,
the posts would fall in but for the wire. There are also lots of smaller cracks
and the whole side of the mountain slid in west of Pleasants [house]. I could
shove my arm in the holes around the posts at the wagon house and cow barn. The
cows are nearly scared to death yet. Everything in the house upstairs was
turned over, even to the wardrobe which brought down a ceiling joist with it .
. .
There was another quite heavy shake last night at two o'clock, but not
enough to knock things down. The telephone will not work between here and
Vacaville, so we have no news from there, but I think the rest of the walls
must have surely fallen in. I was just talking with Mr. Peasants, 9 AM. There
were two more small shocks just now. We may be swallowed up yet. There are lots
of cracks in the hills.
Other reports from Vaca Valley-Pleasants Valley at the time of the 1892
quakes include the following:
In Pleasant Valley, between here (Vacaville) and Winters, the shock was
terrific and it is said not a chimney is standing in the entire valley . . . W.
J. Pleasants' house in Pleasant Valley was wrenched from its foundation (San
Jose Daily Mercury, April 20, 1892).
Falling boulders in Gate's Canyon Thursday morning barely missed the
Alpine schoolhouse one weighing three tons being among the number (Vacaville
Reporter, April 21, 1892).
In Vaca Valley . . . They saw where the trembler had made a small
fissure in the creek. Marysville Weekly Appeal, April 22, 1892, and near J. S.
Pleasants in Pleasants Valley . . . The creek banks contracted shoving one end
of the bridge forward three feet (Vacaville Reporter, April 21, 1892).
West of Vaca Mountains
The active
The effects of the 1892 earthquakes west of the crest of the
The earthquake was scarcely felt in
Mr. Dunton's statement of "no damage" in
Nathan Hagard has just driven in from
In Pope Valley northwest of Berryessa Valley, the April 19, 1892 event
was reported as "no damage done, not even the falling of a chimney,"
and the April 21, 1892 event only as setting "household things to rattling
and dancing" (St. Helena Star, April 29, 1892). Thus, it seems apparent
that the effects of the earthquakes diminished rapidly along the eastern
boundary of Yolo and Solano counties and appears to preclude the possibility
that a fault west of the
West of Winters
The observations by S. B. Dunton of Winters constitute some of the most
descriptive material encountered concerning the geological effects of these
earthquakes in the area west of Winters. He gives the following description of
the effects of the earthquake shock on the cement grade west of Winters. The
following account, titled EARTHQUAKE FORCE---Great Boulders Leave Their Beds
and Crash Down the Mountains, was published in the
I was on the cement grade when the
The "cement grade" corresponds to the present
A subsequent article by S. B. Dunton was published in the Winters
Express,
. . . I have been asked to say something in regard to the causes of our
recent awful visitation . . . I see that Professor Davidson thinks that the
Berryessa valley is the focal center of our great shocks. The writer is
somewhat familiar with the mountain structure west of Winters, and is willing
to admit all that Professor Davidson says as to the geological status of
Berryessa valley and Putah canyon, still there are other geological factors
that stand out with salient clearness to the geological observer. We hear of
convergent lines from the focal center of greatest disturbance. There is no
focal point of greatest seismic disturbance in this section, so fearfully
shaken, still there is a central or base line of greatest violence in our
recent quakes. This is the line of black basaltic rocks four miles west of
Winters. This line varies in width from a few rods to one fourth of a mile, and
follows the general trend of the mountains on the east for a distance of 25
miles that we know of. The black rocks at the Seeley place in the lower Putah
canyon are on this line. Putnam's Peak is of basalt. Vacaville is directly on
this fracture line of basalt; Capay is very near it, and Esparto is not far
away.
Professor Davidson's statement to which Mr. Dunton responded was not
located. However, his apparent belief that
Esparto; April 23; the people of Esparto are very uneasy. Agent Coates
has a telegram in which it is announced that Professor Davidson has predicted
that a severe shock will occur this afternoon, and that
Another article by Dunton was published in the Winters Express of
EARTHQUAKES---Editor Express: - Three weeks ago I wrote an article for
the Express upon earthquakes. Since then a number of intelligent people have
importuned me to write again . . . in the issue of that journal (Dixon Tribune)
of May 27, 1892, Reverend Mr. Hemphill, of Dixon, in a very intelligent,
deferential and respectful manner, takes exceptions to my ideas of seismic
disturbances. The reverend gentleman says that I opposed the ideas of Professor
Davidson, of the Lick Observatory. In this he is just a little mistaken. I
admitted all which Professor Davidson had said, as to the geological status of
Berryessa valley and Putah canyon. I only dissented from the Professor's theory
that Berryessa valley was the focal center of greatest seismic disturbance. And
now, for the "evidences" along that line:
The writer was one of a party who removed the bowlders from the Putah
canyon road after each of the two heaviest shocks, and knows whereof he writes.
He was in Putah canyon during the second great shock. All of the great bowlders,
which came crashing down the mountain sides, were in the lower canyon. There
were not any rocks in the road at the "Devil's Gate," [present site
of
Dunton was obviously observant and his correlation of the "focal
point of greatest force" with a geologic formation trending southerly
toward
Further evidence of violent shaking within the hills west of Winters is
indicated by the following accounts:
Many people drove over (to Winters) from
West of here (Winters) about three miles, an acre of ground slid into
the creek. On the county road this side of the cave there are great cracks in
the ground (San Francisco Chronicle, April 20, 1892).
Up the canyon the road is chocked up with boulders dislodged from the
hillsides. In one place an acre of ground slid into the creek, in the creek are
many fissures caused by the quake, from some of which gas is hissing forth
(Solano Republican, April 22, 1892, p. 3)
Up the Berryessa road the passage is blocked by immense boulders, some
weighing several tons. They were thrown with mighty force down the hillsides
into the road. (It is near this point where the rents in the road were noticed.)
From all around came reports of wells filling up with caving earth (Sacramento
Evening Bee, April 19, 1892, p. 1).
A
Finally, a most descriptive and interesting account:
I drove over with Mr. Devilbiss this morning to look at the geological
changes effected by the earthquake. To the west and south of the town (Winters)
runs Putah Creek, which in the summer is an insignificant stream, but in winter
is a raging torrent, covering a bed a quarter of a mile in diameter [width]. It
is along the line of this creek and in its bed that the last shock seems to
have originated. There are no such ghastly rents emitting gas and steam as have
been described by imaginative and verdant young pencil-sharpeners on the
strength of some frightened rustic's statement, but there are undoubtedly a
number of cracks rapidly closing up and holes from which volumes of water were
ejected at the time of the last quake. The water had evidently gained admission
laterally, and been squeezed out as the earth collapsed after the wave passed
by. An eyewitness furnished a brief but vivid description of the passage of
this wave on Thursday (April 21) morning. He said that he was cultivating a
field a little to the west of the Devilbiss residence (about one mile west of
Winters) when he noticed that the cultivator, on which he was riding, plunged
violently. At the same moment, there was a loud, roaring noise, and cloud of
dust sweeping rapidly along toward the town of
Surface waves travel at a velocity of approximately 3 kilometers per
second. A singular wave or wave train would, therefore, travel the mile or so
from "just west of" the Devilbiss residence to Winters in only about
1 second. Damage at the Devilbiss home and that at Winters would, therefore,
occur almost simultaneously. The observer's comments, however, relate to the
"noise" from the damage as the wave(s) progressed toward and arrived
at Winters. Since sound travels at a velocity of about 300 meters per second,
some 7-8 seconds would lapse between the time an observer "just west
of" the Devilbiss residence (assume one-quarter mile) would hear the noise
from damage at the Devilbiss house and the time he heard noise from damage at
Winters.
CONCLUSIONS
From these various accounts, there appears little doubt that the source
area of the April, 1892 events and, presumably, the entire earthquake sequence
lies in the hills west of the lower
From the same general appearance of things . . . , there seems to be
little doubt that the shock originated in the foothills on the west side and
travelled in a wave 20 or 30 miles long directly to the Sacramento River
(Morning Call, April 23, 1892).
These data suggest further that the source area was located east of the
crest of the
From the numerous accounts, the most intense shaking occurred in the
area generally bounded by
This study supports the earlier conclusion by Dale (1977) that the
source area of this earthquake sequence lies within the hills bordering the
valley west of
Within this area possible sources of the 1892 earthquake sequence
include:
a) an unrecognized thrust fault or faults related to the development of
folds along the western margin of the Great Valley, a source similar to that
which produced the 1983 Coalinga earthquake,
(b) a concealed fault within the
(c) a bedding plane fault within the steeply dipping
The significance of the Vacaville-Winters earthquakes has become more
apparent since the 1983 Coalinga earthquake focused attention on the seismic
hazard associated with the western margin of the
REFERENCES
Bailey, T. L., 1931, Geology of the Potrero Hills and Vacaville region:
University of California Publications Bulletin Department of Geological
Science, v. 19, plate 39.
Brooks, Bruce, 1962, Geological map of Capay-Wilbur Springs, Map Sheet
No. 4, Geologic guide to the gas and oil fields of northern
Bryan, K., 1923, Geology and ground-water resources of
Bryant, W. B., 1982, Midland fault zone: California Division of Mines
and Geology Fault Evaluation Report FER-133, July 30, 1982.
Dale, D. C., 1977, California earthquakes of April 19-29, 1892 in Short
contributions to California Geology: California Division of Mines and Geology
Special Report 129, p. 9-21.
Eaton, Jerry P., 1986, Tectonic environment of the 1892
Vacaville/Winters earthquake, and the potential for large earthquakes along the
western edge of the
Ellsworth, W. L., Olson, J. A., Shijo, L. N., and Marks, S. M., 1982,
Seismicity and active faults in the eastern San Francisco Bay region in
Proceedings Conference on Earthquake Hazards in the Eastern San Francisco Bay
Area: California Division of Mines and Geology Special Publication 62.
Helley, E. J., and Barker, J. A., 1979, Preliminary geologic map of
Cenozoic deposits of the Guinda, Dunnigan, Woodland, and Lake Berryessa
quadrangles, California: U. S. Geological Survey Open-File Report 79-1606,
scale 1:62,500.
Helley, E. J., and Herd, D. G., 1977, Map showing faults with Quaternary
displacement, northeastern San Francisco Bay region, California: U. S.
Geological Survey Miscellaneous Field Studies Map MF-881, scale 1:125,000.
Kirby, J. N., 1943, Rumsey Hills area in Jenkins, O. P. editor, Geologic
formations and economic development of the oil and gas fields of California:
California Division of Mines Bulletin 118, p. 601-605.
Kirby, J. N. and Crook, R. H., 1934, Unpublished geological map of the
Winters-Capay area: Standard Oil Company of
Jennings, C. W., 1975, Fault map of California with locations of
volcanoes, thermal springs, and thermal wells: California Division of Mines and
Geology, Geologic Map Data Series, Map No 1, scale 1:750,000.
Real, C. R., Toppozada, R. T., and Parke, D. L., 1978, Earthquake
epicenter map of
Reynolds, S. N., and Reynolds, S. T., 1963, Midland fault, an Eocene
subsurface fault, Delta area, California: American Association of Petroleum
Geologists Bulletin, v. 47, no. 9, p. 1775.
Sims, J. D., Fox, K. F., Jr., Bartow, J. A., and Helley, E. J., 1973,
Preliminary geologic map of Solano County and parts of Napa, Contra Costa,
Marin, and Yolo counties, California: U. S. Geological Survey Miscellaneous
Field Studies Map MF-484, scale 1:62,500.
Steinbrugge, K. V., Schader, E. E., Moran, D. F., 1975, Building damage
in San Fernando Valley in Oakeshott, G. B., editor, San Fernando, California,
earthquake of 9 February, 1971: California Division of Mines and Geology
Bulletin 196, p. 323-353.
Thomasson, H. G., Jr., Olmsted, F. H., and LeRoux, E. F., 1960; Geology,
water resources and usable ground-water storage capacity of part of
Toppozada, T. R., Real, C. R., and Parke, D. L., 1981, Preparation of
isoseismal maps and summaries of reported effects for pre-1900
Wagner, D. L., Jennings, C. W., Bedrossian, T. L., and Bortugno, E. J.,
1981, Geologic map of the Sacramento quadrangle: California Division of Mines
and Geology Regional Geologic Map Series, Map No. 1A, scale 1:250,000.
Wagner, D. L. and Bortugno, E. J., 1982, Geologic Map of the Santa Rosa
quadrangle: California Division of Mines and Geology Regional Geologic Map
Series, Map No. 2A, scale 1:250,000.
Willis, Bailey, 1923, A fault map of California: Bulletin of the
Seismological Society of America, v. XIII, no. 1.