Archaeoseismology and Palaeoseismology in the Alpine ... - Tierra

1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology
ARCHAEOSEISMOLOGICAL APPROACH ON STONE HERITAGES IN GYEONGJU
AREA, SE KOREA
K. Jin (1), M. Lee (1) and Y.S. Kim (1,*)
(1) Dept. of Environmental Geosciences, Pukyong National University, Busan 608‐737, KOREA. * ysk7909@pknu.ac.kr
Abstract: According to historical records, the Gyeongju area has significantly been affected by earthquakes. Recently, a fallen
carved Buddha statue was found in Gyeongju. Based on the artistic style of the Buddha, the carving age of the Buddha statue
is accidentally coincided with the time of the earthquake in 779 A.D. Therefore, the possibility of interrelationship between the
fallen Buddha statue and the 779 earthquake was examined, and its original location and direction were restored. For these
purposes, the fracture patterns within the fallen Buddha statue and the surrounding outcrop were compared. Consequently,
they are well matched if the fallen Buddha statue is rotated back 20° clockwise supposing its upright position. Although we can
not sure about the consistency of the timing between the falling of the statue and the 779 earthquake, the Buddha statue
must be fallen down by any episodic forces. Other possible earthquake damages are shown on some other historical heritages
in this area and also reported in historical records. According to the recent geological and archaeoseismological studies, the
Gyeongju area might not be free from future earthquakes hazards.
Key words: historical heritage, archaeoseismology, Gyeongju, earthquake
INTRODUCTION
The Korean peninsula has been considered to be
relatively tectonically safe compared with neighboring
countries such as Japan and Taiwan, because it locates
within the Eurasian intracontinental region. However,
many Quaternary faults have recently been reported
along the Yangsan and Ulsan faults, major tectonic
features in SE Korea (Fig. 1). In particular, historical
records for the Gyeongju area, one of the oldest capital
cities in Korea, demonstrate that seismic events have
significantly affected lives and properties of this city. The
study area is a useful place for paleoseismological studies,
because it contains many historical heritages. For
example, the 779 earthquake reported in a famous
historic book, Samguksagi, had an inferred magnitude of
M=6.7 and resulted in over one hundred causalities and
many destructions of buildings (Lee and Na, 1983; Lee and
Jin, 1991; Lee, 1998). Other earthquake damages were
also reported in historical records. Therefore, the aim of
this study is examining the affects of paleoseismological
events recorded on cultural heritages in Gyeongju area.
GENERAL GEOLOGY
The basement of the study area consists of Cretaceous
sedimentary rocks forming part of the Gyeongsang Basin,
which is intruded by Cretaceous and Tertiary igneous
rocks (Fig. 1). The study area, Gyeongju city, is located
around the junction between the Yangsan and Ulsan
faults. The geometry of the intersection between the
Yangsan and Ulsan faults is quite similar to the simulated
model of λ‐fault (Du and Aydin, 1995) and reported small
scale λ‐fault (Kim et al., 2000). Recently, more than 20
Quaternary faults have been reported around the
Yangsan and Ulsan fault system, which are the major fault
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system around the Gyeongsang Basin (Lee and Jin, 1991;
Kyung and Okada, 1995; Jang, 2001; Kim and Jin, 2006).
These indicate that the study area is a potential area to be
affected by high earthquake activities.
Fig. 1: Location and geological maps of the study area (from Jin et
al., in press).
RESTORATION OF THE ORIGINAL POSITION OF THE
FALLEN BUDDHA STATUE
In May of 2007, a fallen rock with carved Buddha statue
was discovered, which was resting on the 45° slope of the
Yeolam valley, Gyeongju (Fig. 2). The Buddha statue was
carved on Cretaceous granite. Based on the artistic style
of the Buddha statue, the construction age of the Buddha