Trees may suffer damage during major earthquakes

due to shaking and faulting of the ground

beneath them. External effects, such as topping,

root and limb damage, and scars may result in a

temporary reduction in the width of their annual

growth rings. Tilting and changes in environmental

factors, such as light, space and water availability

may initiate asymmetric growth. Dendrochronologic

techniques enable dating of such growth anomalies,

and hence earthquakes

Meisling, Kristian E.

Sieh, Kerry E.

Caltech Authors - Main

THE EFFECT OF THE 1857 FORT TEJON EARTHQUAKE 
ON TREES NEAR WRIGHTWOOD, CALIFORNIA 
Kristian E. Meisl ing and Kerry E. Sieh 
Division of Geo ,logical and Planetary Sciences 
California Institute of Technology 
Pasadena, CA 91125 
INTRODUCTION 
Trees may suffer damage during major earth-
quakes due to shaking and faulting of the ground 
beneath them. External effects, such as topping, 
root and limb damage, and scars may result in a 
temporary reduction in the width of their annual 
growth rings. Tilting and changes in environmental 
factors, such as light, space and water availability 
may initiate asymmetric growth. Dendrochronologic 
techniques enable dating of such growth anomalies, 
and hence earthquakes. 
To determine whether or not trees contain 
useful records of pre-historic earthquakes In 
southern Ca I i torn i a, we cored five trees a I ong the 
1857 break of the San Andreas fault near Wrightwood, 
California. Sampling was neither systematic nor 
exhaustive, since we restricted sampling to conifers 
recognized during the course of earlier geologic 
studies along the fault trace. We extracted sample 
cores with both power and manual increment borers. 
Dates were determined by co~nting annual rings. 
The width of each was measured and plotted against 
its growth year. We examined all significant depar-
tures from normal growth trends and tried to inter-
pret them in light of the 1857 earthquake and other 
known environmental factors. 
THE TREES 
A healthy Jeffrey Pine, the Sidehi II Bench Tree, 
is growing astride the San Andreas fault on a fault-
related sidehi II bench northwest of Big Pines (Figure 
1). A core taken from the northwest side of the tree 
reveals a scar involving the growth rings of the 
years 1855-57; the 1856 and 1857 rings are missing 
a I together (Figure 2, WRW 35). In other cores a 
growth minimum is evident in 1857 (Figure 2 WRW 36). 
The ring-ratio plot CSE/NW), calculated by 
dividing the ring widths on the southeast side of 
the Sidehi II Bench Tree by correlative ring widths 
on the northwest side, displays two conspicuous 
anomalies (Figure 3). The ring ratios are close to 
1.0 except during the ten years following 1857 and 
during the twenty years starting about 1960. The 
first anomaly we attribute to damage to the northwest 
side of the tree during the 1857 earthquake. The 
second anomaly Is probably due to an increased growth 
rate on the southeast side of the tree resulting from 
the removal of a nearby competitor, the Stump Tree. 
A few meters southeast of the Sidehi I I Bench 
Tree, and a meter northwest of the fault zone, lies 
the stump of a White Fir dubbed the Stump Tree. A 
part of the tree's crown, discovered nearby, suggests 
that the tree was never topped and originally 
67 
measured a little more than 23m in height. The 
Stump Tree shows a dramatic reduction in ring width 
beginning 101 years before it was felled (Figure 4). 
Recovery from the trauma took about 25 years. 
According to RangerS. R. Carbaugh (pers. comm.), the 
Stump Tree was probably ki lied during a "sanitation 
salvage" logging program in about 1957-58. If the 
ring record is plotted so that the last ring dates 
from 1958, the slowdown begins in 1857. Ki II ing of 
the Stump Tree in 1958 is consistent with the sudden 
burst in growth on the southeast side of the Sidehi I I 
Bench Tree beginning about 1960 (see Figure 3). We 
Figure 1. Sidehil I Bench Tree. Stump Tree hidden 
by brush in foreground. 
68 
E 
E 
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1-
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z 
a:: 
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a:: 
(.,!) 
z 
a:: 
7 
6 
5 
4 
3 
2 
210 
-"' 0::3:: 
<tc:: ~ 3:: • 
,----, /1 
II 
I I 
I I 
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I I 
J,._l I 10 I I ~ 11 ~\ ~ I I I I ! I I 1 I I I I I It 
I,... It 
I I I 
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---- WRW 36 (NW) 
-- WRW 35 (SE) 
o~-~,8~4~o-~-~,~86~o--L--~,8~8~o-~--,=9~oo~-L--~~--L--,~9~4o~-~-~~--L--,~98o 
DATE A.D. 
Figure 2. Sidehil I Bench Tree ring width. 
2.5r-----r--.-------,r------r---r------.-----.--r-----r----.------,r------r---r------.---, 
2.0 
210 
-"' 
1.5 0::3:: etc:: ~3:: 
,----, 
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0.5 
o~-~----~-~~-~-r--~--~--,-9~oor---~--,9~2~o-~~-,-9~4or---~--,9~6-o--~--,~980 
DATE A.D. 
Figure 3. Sidehi II Bench Tree ring ratio. 
were not successful in precisely dating the Stump 
Tree records by correlation with the Sidehi I I Bench 
Tree; but, in I ight of the evidence presented herein, 
it seems likely that the Stump Tree suffered root 
and/or limb damage during the 1857 earthquake. 
In Wrightwood, a pair of Jeffrey Pines are 
located on a low, linear mound southeast of the 
engineered levee of Heath Creek (Figure 5). They 
lean away from each other and show a pronounced 
asymmetry of both trunk and crown. Bends occur in 
the trunks of both the Leaning Tree and the Leaning 
Companion Tree. The lower 7.5 to 12m of the Leaning 
Tree ti Its 1r to the northwest; above 12 m the trunk 
ti Its considerab ly less. The Leaning Companion Tree 
ti Its 13• to the southeast below an abrupt bend in 
the trunk at about 3.5 m; above this bend the trunk 
is nearly vertical. These effects could be the 
result of mutual competition for space and light, but, 
because both trees are rooted in the fault zone, we 
suspected that the ti Its might also be related to the 
1857 ea rthquake. Eight cores were taken from the 
Leaning Tree and one from the Leaning Companion. 
Different core records within the Leaning Tree 
correlated well with each other, although attempts to 
corre late with ring records from other trees were 
unsuccessful. The oldest ring penetrated by cores of 
Figure 5. Leaning Tree and Leaning Companion Tree. 
69 
the Leaning Tree formed in 1846; the tree was 
probably about 1.5 m tal I in the late 1830's. One 
core on the northwest side shows a slowdown and 
recovery anomaly beginning in 1856 (Figure 7, WRW 18). 
The ring-ratio plot (SE/NW) shows a 20-year positive 
anomaly beginning in 1856, followed by a long 
sustained negative anomaly (Figure 9) . 
Morphological features and ring data for both 
the Leaning Tree and the Leaning Companion Tree are 
cons istent with a single tilting event in 1857. The 
Leaning Tree was about 20 years o ld, 10m high and 
about 15 em in diameter at the time of the earth-
quake. We propose that the 20-year ring-ratio 
anomaly reflects trauma caused by root or limb 
damage suffered during fault slippage underfoot in 
1857. After recovery, the tree's shifted center of 
gravity led to increased growth on the northwest 
side relative to the southeast side. The competitive 
influence of the Leaning Companion Tree heightened 
the tendency. The asymmetry of the Leaning Tree 
actually began in 1856. According to avai !able 
rain records, 1856 was a moderately dry year, but 
response to water shortage should not have been 
asymmetric. Although it is tempting to interpret 
this early onset of trauma as evidence of root 
damage caused by creep during the year preceding 
the earthquake, there are not sufficient data to 
warrant this conclusion. Pest and wind damage might 
have resulted in asymmetric growth and thus cannot 
be ruled out. 
The Leaning Companion Tree is rotten in the 
center and the rings older than about 1869 are not 
preserved. It is not clear how many years of early 
record are missing, but our estimates place the 
Leaning Companion Tree at a height of 1.5 m during 
the early 1840's. Thus the tree was about 15 years 
old, 4 m high and about 10 em in diameter in 1857. 
Morphological features and ring data tor the Leaning 
Companion Tree are also consistent with a single 
tilting event in the mid-1800's through which only 
the outer rings survived intact. Considered 
together, the Leaning Tree and the Leaning Companion 
Tree offer compel ling evidence of a single tilting 
event in 1856-57. 
The Lone Pine Canyon Road Tree, in contrast, 
shows no effect of the 1857 earthquake (Figure 8). 
It is situated just south of Lone Pine Canyon Road, 
west of the saddle at the head of Lone Pine Canyon. 
It lies about six meters southwest of the main trace 
of the San Andreas fault, and was once topped about 
15 m from its base, where three large branches have 
subsequently grown. The tree appears to have lost 
its entire crown at the time of the topping. 
The Lone Pine Canyon Road Tree was about 1.5 m 
high in 1749. A slight southwestward ti It of the 
lower 1.5 m of the trunk suggests a tilting event 
in the mid-1700's. A core taken on the northeast 
side shows a dramatic s I ow down beginning in 1834 
(Figure 6). The core shows no obv ious effect of the 
1857 earthquake. Either the Lone Pine Canyon Road 
Tree was not serious ly damaged during the 1857 earth-
quake, or the damage sustained in 1834 so limited the 
tree's growth that the effect of later damage cannot 
be recognized. We favor the second hypothesis, and 
cite as evidence the anomalously long 55-year 
recovery pe riod that follows the topping event (see 
Figure 6). No large or moderate earthquakes are 
recorded for this region In 1834, so we conclude that 
the tree was probably topped by I ightning or wind in 
1834. 
70 
o~--~---17~5o----~--1~8o-o--~----18~5o--~----~--~--~~--~--2~ooo 
DATE A.D. 
Figure 4. Stump Tree ring width. 
Figure 6 . Lone Pine Canyon Road Tree ring width. 
---- WRW 17 (SE) 
10 -- WRW 18 (NW) 
9 
8 
_7 
E 
E 
::Z::6 
....... 
C) 
~ r-
<.!)5 on 
z 
a:: 
4 
3 
2 
OL---~18~5~0----~--~1~8~70~---L--~18~9~0----L---~1~91~0----~--~19~30~---L--~19~570 ____ L_ ___ 1~97~0----~ 
DATE A.D. 
Figure 7. Leaning Tree ring width. 
1.6 
0.4 
0·2L_-~18~5o~--L-~,8~7o~-~---,~8~~--L--~1~91~o---L_--,,f~~o---L_-~n----L---.,~--~ 
DATE A.D. 
Figure 9. Leaning Tree ring ratio. 
71 
72 
Figure 8. Lone Pine Canyon Road Tree. 
CONCLUSION 
Clearly, no seismic event should be postulated 
on the evidence of one tree alone. It would be an 
embarassing mistake to attribute to a great earth-
quake damage actually produced by a mere I ightning 
strike or a strong gust of wind! If an undocumented 
earthquake is suspected, many trees should be 
examined and evaluated for consistency before the 
event is formally proposed. Further study of 
ring-ratio plots may help establish criteria for 
distinguishing damage due to earthquakes from 
damage due to other natural agents. 
Our preliminary survey indicates that the 
1857 Fort Tejon earthquake was indeed recorded by 
several conifers on or near the fault rupture. Of 
five trees sampled in Wrightwood, four show ' damage 
effects and/or growth anomalies attributable to the 
1857 earthquake. Our success in recognizing the 
effects of the 1857 event in these trees, despite 
capricious sampling, suggests that a suite of older 
trees may contain a valuable "dendroseismological" 
record of large pre-historic earthquakes in 
southern California. 


The Effect of the 1857 Fort Tejon Earthquake on Trees near Wrightwood, California

https://authors.library.caltech.edu/98540/1/Meisling_1979p67.pdf

The Effect of the 1857 Fort Tejon Earthquake on Trees near Wrightwood, California

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