Journal of Natural Disaster Science, Volume 25, Number 2, 2003, pp65-74

Eastern Asia Geological Hazards Map: Paper and Digital Versions
Hirokazu KATO, Koji WAKITA and Joel C. BANDIBASNational Institute of Advanced Industrial Science and Technology (AIST)(Received for 30. Jun., 2003 and in revised form 4 Nov., 2003)

ABSTRACTThe Eastern Asia Geological Hazards Map (paper version) and Interactive Geological Hazard Map of East andSoutheast Asia with GeoHazardView (digital version) respectively were published in 2002 and 2003 by the
Geological Survey of Japan (GSJ), AIST. These constitute the first attempts to compile small -scale hazard mapping focused on the geological hazards in eastern Asia. The paper version consists of a geological hazards map ofendodynamic origin that includes seismic hazards in particular tsunami and volcanic ones; one sheet of hazards of
exodynamic origin partly induced by human activities such as landslides, coastal erosion, and deposition; one
sheet explaining the legends, and an explanatory pamphlet. Because of paper version limitations, a digital CDROM version was produced to make hazard information readily available both to geologists and the general public. In order to mitigate geological hazards, the general public also needs to be well informed about the problems.
The CD-ROM presents all the collected geological hazard information in the mapping project in an interactive
way by the use of newly developed GeoHazardView software. The user can access, view, manage, update andenlarge or reduce the scale on the screen at will. To handle both types of maps easily and for better user understanding, the geological hazards are summarized.

1. INTRODUCTION
Damage caused by natural disasters has been increasing andbecome more serious world-wide, especially in Asia, because ofcomplicated and active natural environments. Such damage is further aggravated by countries weak and vulnerable social conditions which have been worsened by rapid, uncontrolled socio-economic development. During the latter half of the 20th century, 70
percent of the approximately 5 million people who were disastervictims were in Asia. Mitigating of the effects of natural disasters
therefore is a priority in Asian countries. One important aspect of
mitigating damage is to make information about natural disasters
readily available; not only to policy makers, planners, and professionals but to the general public as well. By doing so, communities will be better informed about devising measures to minimize
the loss of lives and the economic impact of natural disasters.
Natural hazard mapping and development of relevant databases areindispensable in such undertakings. Distribution of both paper anddigital versions of such maps is very important today for people togain such information as soon as possible because Internet
Technology is rapidly developing.
During 1992 the 29th International Geological Congress (IGC)
in Kyoto, Japan, Japan proposed an international scientific program for world-wide natural hazard mapping. An international
forum next was held in Tsukuba, Japan in 1993 to implement this
proposal (Kato, et al. ed., 1994; Kato, 1998). The result of thisforum was formulation of the Eastern Asia Natural Hazards
Mapping Project (EANHMP) in the GSJ, focusing on geologicalhazard mapping in the eastern Asia region as the first step. This
started in 1994 with the cooperation of the international community. The project was endorsed by the International Decade for

Natural Disaster Reduction (IDNDR), the Coordinating Committee
for Geoscience Programmes in East and Southeast Asia (CCOP),and the Commission for the Geological Map of the World(CGMW). Its implementation is shown in Table 1. Consequently,
the Eastern Asia Geological Hazards Map (1:7,700,000) was published in 2002 (Kato and EANHMP, 2002). Although some of theinformation on geological hazards collected in the project had
already been published (See Kato, et al., ed., 1994; Kato andShimazaki, ed., 1997; GSJ ed., 1998, Kato and EANHMP, 2002),
not all could be fully described by means of printed media. To
make comprehensive information about geological hazards readily
available and accessible to a wide range of users, an interactive
digital version of the map, distributed in CD-ROM (GSJ, AIST,
2003) was produced. We introduce the paper and digital versionsof this hazard map and provide a brief summary of the geologicalhazards in the eastern Asia region to help users gain a better understanding of the usefulness of these maps in efforts to mitigate disaster damage.
2. EASTERN ASIA GEOLOGICAL HAZARDS MAP
2.1 Composition(1) The paper version of the geological hazards map consists ofthree sheets and an explanatory note. The first and second sheets
give historical records of each hazard event with the backgroundgeology and qualitative risk probability (prone area). The third
sheet presents the legend and brief explanations. The first sheet
mainly shows geological hazards of endodynamic origin such as
seismic ones, including tsunami and volcanic hazards. The second
sheet mainly shows geological hazards of exodynamic origin suchas landslides, coastal erosion, and deposition and related phenome-

KEY WORDS: geological hazard, hazard map, seismic hazard, volcanic hazard, landslide, coastal erosion, eastern Asia

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H. KATO, K. WAKITA AND J. C. BANDIBAS

Table 1

Implementation of the Eastern Asia Natural Hazards Mapping Project (EANHMP)

na. The small-scale map also presents information about regionalrisk potential, remote source hazards such as tsunami and regional
volcanic ash fall, as well as the vulnerability of a given region tocompounded hazards.
(2) The digital version of the map (Interactive Geological Hazard
Map of East and Southeast Asia with GeoHazardView) is distributed as a CD-ROM which has an interactive version of the geological hazards map. The aim of the digital version is to provide more
extensive information about geological hazards than is possible in
the paper format. The geological hazard maps and related information are presented in an interactive way by means of
GeoHazardView software programmed by Joel C. Bandibas of the
GSJ, AIST. This CD-ROM has digitized geological hazard maps
as well as related geological hazard information such as the data on
individual events, photographs of volcanoes, etc. These data canbe accessed, managed, viewed, and updated only by using
GeoHazardView software installed and run under the Microsoft
Windows operating system. The user has the option to enlarge or
reduce the scale on the screen using that software. When the user
starts the GeoHazardView, the hazards selection mode is indicatedon the screen. Concrete individual usage is described in each hazard section as follows.
2.2 Legend of the printed hazard map and its digital version
Small-scale and regional hazard maps that show several geological hazards together against the background of the area s geology and topography and their digitized map are the first trial in thehazard mapping of the world. Therefore it is first necessary to
explain the legend and how to compile the maps.

(1) Geological and Topographical BackgroundThe characteristics of geological hazards, their occurrence,
type, and susceptibility, are closely related to the geological, tectonic and topographical settings. In this hazard map, the exaggerated topographic features only are represented by shading insteadof contour lines because the scale is so small.
The geological legend roughly depends on the stiffness of theground, as shown in the dialog box of Fig.1 which shows an example scene from the digitized map presenting the main part ofJapanese archipelago.
a) Sedimentary rocks: S1 shows mainly hard pre-Neogene sedimentary rocks; S 2 mainly consolidated Neogene sedimentaryrocks; S3 mainly semi-consolidated Pleistocene deposits including
some undifferentiated Holocene sediments; and S4 mainly unconsolidated Holocene deposits.
b) Volcanic rocks: V 1 shows mainly hard and massive preNeogene volcanic rocks; V 2 consolidated Neogene-Pleistocene
volcanic rocks; V3 mainly Quaternary volcanic rocks related torecent volcanic activities, and V 4 undifferentiated NeogeneQuaternary volcanic rocks.
c) Pre-Quaternary hard rocks such as plutonic, metamorphic,
ultramafic and associated basic rocks are grouped into one category.
Tectonic features also affect geological hazards. In inland
areas, geological faults with lengths roughly longer than 100 km
are represented by solid black lines, and inferred faults by broken
black lines. Red lines represent active faults, major faults that atleast cut Quaternary deposits, and inferred active faults are shownby broken red lines. Fold axes are omitted to avoid complexity. In

EASTERN ASIA GEOLOGICAL HAZARDS MAP: PAPER AND DIGITAL VERSIONS

offshore areas, plate tectonic settings and topographic featuresreflect accumulated tectonic movements are shown, in particular
subduction boundaries that are divided into two groups, erosion
and accretion types, because of the effects of gravitational slides
on the sea bottom.
(2) Seismic Hazards
Earthquakes are classified by magnitude (M decided by theJapan Meteorological Agency), focal depth, and the number ofcasualties. An earthquake with a magnitude larger than M7.0 isshown by a large circle on the map; one with magnitude between
M6.0 and M7.0 is shown by a medium circle, and one of unknown
magnitude by a small circle. An earthquake with a focal depth lessthan 10km is shown in red, one with a focal depth between 10 and
70km in dark green, one with a focal depth deeper than 70km in
purple, and one whose focal depth is unknown in black. The number of casualties is shown by a graded sector inside of a circle. In
the digital map, if the user clicks on each circle showing an earthquake, individual earthquake information: latitude, longitude,
country of the epicenter, name of the earthquake, date of occurrence, number of casualties, focal depth, magnitude and if tsunami
occurred appears. Furthermore, the circle clicked is magnified andpulsates, the maximum magnitude scale being shown by the colorof the center. Figure 2 shows an example screen on the digital
map. All the collected data are not always shown on the map. For

Fig. 1

67

example, in China, earthquakes with magnitudes of less than M7.0
are omitted to avoid complexity. A double circle signifies association with a single tsunami and a triple circle with multiple tsunami
events in the past. Because coastal areas attacked by tsunami inthe past may again be devastated in the future, where sufficientcountermeasures have not taken, locations are called the tsunami
prone areas and represented by blue along the shorelines shownon the map. In the digital map, the user has the option of measuring the distance between two points by using the pointer mode.
This function allows the user to determine the distance (kilometersand miles) jbetween the offshore epicenter of an earthquake andthe closest coast on the screen. The arrival time of a tsunami canbe calculated if the speed of the tsunami wave. Earthquakes associated with surface ruptures which directly damage man-madestructures and which may occur repeatedly at the same adjacentsites also are represented separately. On the digital map, by pulsating the symbol the user can show specified earthquakes selected byrange of occurrence times, magnitude, focal depth, locality, numbers of casualties, etc.
(3) Volcanic Hazards
Legends for volcanic activities related to the type and recurrence of volcanic hazard are shown by various symbols on the map(Fig.3). A triangle indicates the location of an active volcano, andits size the intensity of volcanic activity. If the user clicks on a tri-

Geological view of the hazard map (CD-ROM version)

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H. KATO, K. WAKITA AND J. C. BANDIBAS

angle in the digital version, the name of the volcano and detailed
information of its activity will appear. A triangle colored red indicates volcanic activity with magma eruption over the past 2,000
years. Orange triangles indicate there is no record of volcanic
activity. A dot inside a triangle signifies a volcano that is associated with a crater lake and/or snow capped. A circle enclosing a triangle represents a volcano associated with a topographic caldera
depression of a diameter larger than 10 km. Broken purple lines
delineate areas covered by a large-scale volcanic ash falls in thepast 2,000 years. In the overall map, regional ash fall deposit areas
during the eruptions of Baitoushan (Paekdusan), Korea in the 10th
century, Tambora, Indonesia in 1815 and Pinatubo, the Philippines
in 1991 are shown, but they are not presented in Figure 2 because
it shows only the main part of the Japanese archipelago. In thedigital version, the areas of ash fall spread across the screen withtime by means of animation.
(4) Landslide and Related Slope Disasters
Landslides and other slope disasters are the most destructive
geological and geomorphic processes caused by restoration of thegravitational stability of the earth s materials. Such disasters may
also be complicated by human-induced factors that affect the stability of slopes. On this map, only landslide-prone areas areshown, indicated by solid brown areas because of difficulty inquantitatively correlating the susceptibility of landslide occurrence

as proposed by each country s committee. Landslide-prone areas
correspond to so-called high and moderate susceptibility zones inwhich more than 10 deaths have occurred in the past. From qualitative topographical and geological points of view (Fig.4), thesezones may give serious social-economic effects in near future,(5) Coastal erosion/deposition
Changes in natural coast lines depend on balance between thescouring effects of waves and ocean currents and the supply of
sediments which also are affected by human activities. Recently,
as economic development of coastal areas has accelerated, retreatof coast lines due to erosion has worsened.
In this mapping project, country data about coastal changes
could obtained only from China, Japan, and Thailand.
Consequently, such coastal types as rocky coasts, sand and gravelones, sand and muddy ones, coral reef coasts, mangrove ones andartificial coasts are represented instead of quantitative change
rates.
3.

OUTLINE OF GEOLOGICAL HAZARDS IN
EASRERN ASIA

One of the most important ways to mitigate damage by disasters is to enhance awareness of geological hazards and the understanding of them among the public nationally and locally. Because

Fig. 2 Earthquakes and seismic hazard view of the hazard map (CD-ROM version)

EASTERN ASIA GEOLOGICAL HAZARDS MAP: PAPER AND DIGITAL VERSIONS

Eastern Asia communities have common interests about the causes
and effects of geological hazards, it is useful to exchange information about the processes, mechanisms, causes and properties ofsuch hazards, and the countermeasures taken even though eachcountries have characteristic geological and tectonic settings.
Moreover, as some geological hazards directly affect areas thatcross national boundaries, it is useful to know what geological hazards exist in other countries. Small-scale hazard mapping done incooperation with concerned Asian countries and relevant international organizations provides the best means of mutual enlightenment. An outline of the geological hazards present in eastern Asia
is given in order to understand the hazard maps because continental areas, island arcs, and offshore regions have unique geologicalhazard characteristics.
3.1 Geological Hazards in Island Arc regions(1) Seismic Hazards
The island arc regions are located in the most violent seismic
zones, rendering them essentially seismic hazard areas because
subducting ocean plates along the arcs not only directly causeinter-plate earthquakes with fairly deep focal depths but indirectly
cause of intra-plate earthquakes with relatively shallow focal
depths and inland active faulting. Inter-plate earthquakes that
occur in offshore regions often trigger tsunamis even when their69

epicenters are far from the damaged coasts. Consequently, most
coastal regions of the eastern Asia island arcs have more frequently been attacked by tsunamis as compared to those of Asian continent.
The Japanese archipelago, under which four plates collide has
been severely damaged by several types of earthquakes. The Great
Kanto Earthquake (M7.9) of 1923, one of the strongest, mostdestructive earthquakes, is a typical example of an inter-plate
earthquake. It caused a huge number of casualties, approximately
142,000. The same type of earthquake is expected to occur in thenear future along the trenches on the Pacific Ocean side of thearchipelago. The 1891 Nobi Earthquake (M8.0) in central Japan isthe severest example of an intra-plate earthquake caused by active
faulting. The latest earthquake of this type was the 1995
Hyogoken-nanbu Earthquake (M7.2) in southwest Japan, which
resulted in 7,232 casualties, the collapse of more than 140,000
houses, and other types of severe damage such as fires. This earthquake was associated with a 10.5km long earthquake (surface)
fault that appeared along an existing active fault whose recurrent
activity interval is about 2,000 years, and it directly dislocatedhouses (Kato ed., 1995). The Japanese archipelago, there has
about 1,500-2,000 active faults whose recurrent periods of activities range from several hundreds to a few thousand years. A recent
typical tsunami attack in the northernmost part of the archipelago

Fig. 3 Volcanoes and their activities of the hazard map (CD-ROM version)

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H. KATO, K. WAKITA AND J. C. BANDIBAS

was caused by the 1993 Hokkaido Nansei-oki Earthquake (M7.8).
It resulted in 230 casualties and 937 buildings destroyed. Thattsunami, with a maximum run-up height of about 30m, struck 4 to
5 minutes after the earthquake occurred.
Neo-tectonic activity and seismicity also are very high in andaround Taiwan due to the collision of the Eurasian and Philippine
Sea Plates. About 50 active faults extend mainly along the longitudinal axis of the island, and reflect ocean plate motion, but mostare not shown on the map because of their short lengths.
Throughout the 20th century, Taiwan has had several disastrous
earthquakes; those in 1906 (M6.8), 1935 (M7.1), 1941 (M.7.2),
and 1951 (M7.0), which were associated with earthquake surface
faults. The latest intra-plate earthquake was the 1999 Chi-Chi
Earthquake (M7.3-7.6, focal depth 5-10km). It was the result ofreactivation of an active thrust fault with a total length of morethan 90km. Various kinds of ground deformation were concentrated on the hanging wall of that fault (Lee, 2000).
Earthquake activity in several seismic zones in and around thePhilippine archipelago account for more than 3.2 % of the world s
activity and is caused by the very active motion of the western
margin of the Philippine Sea Plate. (Gupta, 1997). Inland, themost active, 1,200km-long Philippine Fault roughly parallels thePhilippine Trench from Luzon Island in the north to Mindanao
Island in the south. It caused repeated M7 class intra-plate earth-quakes during the 20th century. The average recurrence time ofthis left-lateral fault is estimated to be from 1,600 to 5,000 years.
A recent earthquake along the Philippine Fault was the 1990 one ofmagnitude 7.8 which caused not only the collapse many buildings
but the induction of numerous destructive landslides. Even worse,
it is not an exaggeration to say that every earthquake near thePhilippines is soon followed by a tsunami.
Because the 6,000km-long Indonesian seismic belt is under
the influence of the convergence of the Pacific, Indo-Australianand Eurasian plates, the seismicity there accounts for about 10% of
the world s total. An average of about 400 earthquakes occur
annually, ten of which are high magnitude ones. Furthermore,inland, the Great Sumatran Fault, a 1,650 km-long, dextral strikeslip fault zone, accommodates part of the oblique convergence ofthe surrounding plates, causing intra-plate earthquakes. A 300 kmlong seismic gap is estimated along this fault (Bellier et al., 1999).
Tsunami have always been associated with the main shocks
because Indonesia has the longest coast lines in the world, agraben-like basin has developed under the extensional tectonics ofthe sea floor and hypocenters typically occur beneath the sea floor(Simandjuntak, 1995).
(2) Volcanic Hazards
The island arc regions of eastern Asia are located in the circum-Pacific volcanic zone. Interaction between several plates inFig. 4 Landslides and their prone areas of the hazard map (CD-ROM version)

EASTERN ASIA GEOLOGICAL HAZARDS MAP: PAPER AND DIGITAL VERSIONS

the Quaternary has resulted in remarkable volcanic activities
throughout the region. Japan has more than 200 Quaternary volcanoes, of which more than 80 are still active, comprising ten percent
of all the volcanoes in the world. There are about 200 Quaternary
volcanoes, including 21 active ones, in the Philippine archipelago,
and about 129 active volcanoes and 271 volcanic ruins in theIndonesian island arc.
The worst ten volcanic eruptions in Asia, in terms of the number of human lives lost have occurred in Indonesia, with the exception of the 1792 eruption of Unzen volcano in Japan. The eruptionof Tambora volcano in 1815 was the worst, resulting in 92,000
deaths and a massive regional ash fall. Although most volcanic
hazard is restricted to the immediate vicinity of the erupting volcano, the volcanic ash ejected may travel long distances and covera wide area. This can affect the flight of airplanes and disrupt
regional climatic patterns. Some examples of recent volcanic
activities are given hereafter.
In Japan, recent volcanic activities have been vigorous. The
eruptions of the Unzen volcano, Kyushu Island from 1990 to 1995,
resulted in more than 9,000 dome-collapsed pyroclastic flow
events and the deaths of 44 people. In the 2000 eruption of Usu
volcano, Hokkaido Island, the first explosion sent a plume 32,000
meters high and ejected about 130 thousand tons of tephra. That
eruption caused the evacuation of more than 8,000 people for morethan one month. The most recent volcanic eruption in Japan wasthat of Miyakejima, a volcanic island, far to the south of Tokyo,
central Japan. That eruption was associated with a large crater
formed on the summit which has continuously emitted SO2-richvolcanic gas. This caused the evacuation of the island s entire
population (circa 3,800 people) in early September 2001. Even
now in 2003, none of the evacuees have been allowed to return
permanently.
In the Philippines, more than 700,000 people live in theimmediate vicinity of various types of dangerous volcanoes.
Consequently, significant casualties have occurred in such major
volcanic eruptions such as those of the Mayon, Hibok-Hibok, Taal,
Bulusan, and Canlaon volcanoes. The most recent catastrophic
volcanic eruption was the 1991 Mount Pinatubo Plinian eruption incentral Luzon Island. That volcano ejected some 8.4 to 10.4 km3of pyroclastic materials which killed more than 400 people andturned into lahar flows that still pose a continuing threat to central
Luzon Island (Bornas, 2000).
The volcanic disasters experienced in Indonesia are too manyto enumerate, and there are still many active, dangerous volcanoes.
The lava of Indonesian volcanoes is andesitic in composition, i.e.
the explosive type. More than 50% of the world s victims of volcanic disasters have been Indonesians. In the 19th and 20th centuries, numerous killer volcanic eruptions occurred in theIndonesian archipelago in addition to the eruption of Tambora volcano. The eruption of Krakatau volcano in 1883 killed 38,000
people, and the lahars of the eruption of Kelut volcano in 1919
killed 5,000 people. In 1930, Merapi erupted killing 1,369 people
and in 1963 Agung volcano claimed 1,700 lives. Merapi volcano
in central Java erupted again in 1994, the heat cloud killing 32 people (Katili, 1994).
(3) Landslides and Related Slope Disasters
The active tectonic island arc regions also have high potentials
for landslides because the islands consists of vast hilly and moun-71

tainous areas with steep slopes that are made up of various types ofgeological discontinuities and weak, unconsolidated bedrock.
Earthquakes and heavy rainfalls frequently trigger landslides. An
example of an earthquake-induced landslide is one that occurred in
1989 along the Sumatra Fault System and killed 120 people.
Approximately 300 major landslides occur in Indonesia every year,
30 to 40 occurring during the annual monsoon season. Such landslides caused the deaths of several hundreds of people in the latter
half of the 20th century. In recent years, human activities for agriculture and human settlement in hilly and mountainous areas
where are usually on unconsolidated volcanic materials haveinduced debris slides and slumps. An example of a humaninduced landslide is the 1987 one caused by quarrying in West
Sumatra that took 130 lives. A landslide caused by cutting slopes
for the expansion of settlements occurred in 1985 in West Java andkilled 37 people (Siagian, 1998).
In the Japanese archipelago, which is seventy percent mountainous, the occurrence of landslides is strongly affected by geological and tectonic settings. One of the most devastating types ofavalanche is caused by large-scale rapid catastrophic slope failure
sometimes associated with composite volcanoes (volcanic rocks)
and high relief mountainous regions that have Pre-Tertiary accretionary terrains. Another devastating landslide type is caused byslow sliding and creep. It occurs in areas where clayey soil isunderlain by mudstone, tuff, hydrothermal-altered volcanic rocks,
or serpentine. Landslides also occur in semi-consolidated clastic
materials of the Neogene. These areas are associated as well withreactivated slow slides of mudstone and rapid slides of gravels andsandstone. It is characteristic that enormous landslides are closely
related to uplifting that took place during the Quaternary (0.5 to 1
Ma). For example, the 1985 Jizukiyama landslide, which killed 26
people, occurred in central Japan where the mountainous region
shows the highest uplifting that took place during the Quaternary.
That slide was 350 meters wide, 700 meters long, and had a volume of 3.5 x 106 m3. This type of mass movement is associatedwith such geological and tectonic settings as active faulting but inthat case heavy rainfall directly triggered the landslide.
(4) Coastal Erosion/Deposition
Island arc regions have very long coast lines because they arecomprised of many islands. Change in status is balanced by thescouring of waves or ocean currents and by sediments supplied byrivers as well as by human activities. For example, the total coastline length of the Japanese archipelago is approximately 33,000
km. Changes in the 9,500 km sandy coast line are closely related
to littoral drift induced by incident waves and long shore currents.
The advance and retreat of coast lines respectively add up tochanges of more than 1 meter and less than –1 meter per year.
Stable coasts have changes within the 1 to –1 meter per year range.
Tanaka et al. (1993) found that the coast lines of the islands of
Hokkaido in the north and Okinawa in the south of the archipelago, are the most severely eroded coastal areas in Japan. In Osaka
Prefecture, the second largest in Japan, an artificial coast has beendeveloped, and the lengths of its retreating sandy coast line and thenatural sandy coast line are the shortest in Japan. Isobe (2000)
pointed out that the potential for coastal erosion has been very highsince 1978 because of various development projects and industrial
activities in Japanese coastal areas.

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3.2 Geological Hazards in the Continental Region(1) Seismic Hazards
Seismic activity in China is characterized by high frequency,
large magnitude, and extensive distribution. Typical intra-plate
earthquakes cause severe damage because of their shallow focal
depths. Over the past 3,000 years, nearly 10,000 earthquakes haveoccurred in China, 60% of them destructive. The most recent disastrous earthquake was the 1976 Tangshan Earthquake (M7.8)
which claimed about 240,000 lives. The average interval for astrong earthquake with a magnitude of 8 is about 13 years, whereas
earthquakes with magnitudes of 7 to 7.9 occur at 2 to 3 year intervals. On the average, earthquakes with magnitudes of 6 to 6.9
occur every year. According to Ding (1994), in China there havebeen more than 715 earthquakes within the last 90 years, that havecaused about 614,680 casualties. Although tsunami are relatively
rare on the Chinese mainland, in the past, Taiwan frequently experienced tsunamis. Twenty-five tsunami attacks were recorded in
the whole China from 47 B.C. to 1966, 8 to 9 of which weredestructive (Shi, 1995).
In and around the Korean peninsula, seismic activity related totectonic structures such as the Yangsan and Ulsan active faults inthe southeast of the peninsula is not very severe and earthquakes
usually of a magnitude of less than 4 having occurred. Historical
records, however, report a disastrous earthquake in 779 thatclaimed more than 100 lives as well as tsunami in 1643, 1668, and
1681. In 1993, the East Sea tsunami with a maximum run-up
height of 2.57m devastated the eastern coast of Korea.
In Vietnam and adjoining regions, their older tectonic frameworks have been reactivated during recent geologic times because
they have been affected by tectonic movements of the HimalayanIndonesian and West Pacific mobile belts. Seismic activities inNorth Vietnam most frequently are recorded along active NW-SE
trending faults. In the 20th century, there were 2 earthquakes withintensities of 8 to 9 (Ms=6.7) and some 20 earthquakes with anintensity of 7 (Ms=5.0-5.6). Most occurred in mountainous zones,
where the population density is very low and resulted in very low
damage. At present, although the seismic hazard in Vietnam is notsevere, it is expected to worsen because of the rapid expansion ofurban areas and concentration of the population in industrial centers which may be located in high seismic activity zones (Nguyen
Dinh Xuyen,1994; Tran Van Tri, 1997).
Myanmar lies on the border of the Alpine-Himalaya seismic
zone, and historical records show that remarkable earthquakes
have occurred throughout the country, except in coastal areas.
Owing to a low population and the absence of multi-storied buildings and infrastructures, past strong earthquakes did not cause
great loss of property or human lives (Swe, 1994). As the othercontinental countries of Laos, Cambodia, Thailand and(Peninsular) Malaysia are located on ancient rigid blocks in rather
non-active tectonic settings, most have escaped the severe damage.
(2) Landslides and Related Slope Disasters
In Korea, landslides result in an average annual loss of 60
lives. Most are triggered by rainstorms from July to September
and often are induced because construction works have createdunstable slopes. (Lee, 1994).
In China, landslides represent the largest type of slope disasterin terms of scale. Individual landslides have a volume of morethan generally 10,000 m3, and the biggest may have 1 billion m3.

The oldest reported landslide, which occurred in 186 B.C. in
Wudu, central China, killed 760 people. By A.D.1989, the numberof casualties caused by landslides was at least 257,000. Theselandslides generally were triggered by earthquakes, very heavy
rainfall, or flooding caused by the failure of dams (Ding, 1994; Li
and Wang, 1992). Slope disasters brought about by debris flows
also have caused severe damage. A typical recent example
occurred in Dongchuan City, Yunnan Province. From 1965 to
1985, debris flows occurred 10 to 28 times per year on the average,a totally 260 such flows. The average volume of materials transported is about 1 to 3 million m3 per year, sometimes as much as 5
million m3. The primary causes of debris flows are the weak geological and active tectonic settings.
In Vietnam, slope disasters occur in mountainous areas in thenorthern and central regions of the country. Detailed informationon these slope disasters, however, is not available at present.
In Cambodia, landslides also occur in hilly and mountainous
areas but recent attention have focused on landslides along the
Mekong River s banks where social and economic development
has been remarkable. The magnitudes of Cambodian landslides
normally are higher during the rainy season (Boly, 1997).
In Thailand, landslides mainly occur in mountainous regions
owing to a combination of high relief and high precipitation. For
example, the debris flow slide of 1988 in southern Thailand, triggered by a major rainstorm, claimed 100 lives (Harper, 1993). The
most severely affected area lies in a zone of deeply weathered
granitic rocks with a thickness of 1 to 10 m. If the areas damagedby that extensive landslide had not been deforested, the landslidevolume would have been 20 to 30% less.
In Malaysia, excessive precipitation and human activities,
such as road construction, changing the water level of reservoirs,
and mining operations are the main external factors during theheavy rainfall season, many deep-seated slides occur in colluvial
deposits and on some hill slopes with heights of up to 50 meters.
Most of the rockfalls in peninsular Malaysia occur in limestone
hills and rock overhangs along road cuts (Mohamad, 1994).
(3) Coastal Erosion/Deposition
On the Korean peninsula, the eastern coast, comprised of
Paleozoic and Mesozoic sedimentary rocks, is more resistant toerosion than is the western coast comprised mostly of Precambrianmetamorphic systems and Mesozoic granites. The western coast,
total length about 17,300 km, is characterized by gently undulating
and small hilly areas with a large but shallow alluvial plain. It isvery irregular because of the presence of many islands, embayments and tidal flats. In contrast, the eastern coast region is more
mountainous, its valleys being deeply incised and short, and it ischaracterized by curvilinear, steep-sloped headlands. Narrowcoastal plains are present only in and around rivers mouths. At
the mouth of the Nakdong River, since construction of a dike tocontrol water flow, a sand bar near the coast has migrated seaward,
indicative of coastal erosion and a lower supply of channel sediments due to artificial human effects (Lee, 1995).
The continental coast line of China is about 18,000 km long,and there are several thousands of islands. Most coastal cities arelocated in delta areas (Ha, 1995). This is serious because not only
do the deltas protrude into the ocean, submerged deltas are washedaway by strong ocean currents. The old Yellow River delta has thehighest retreat rate of all the coastal deltas in China, erosion

EASTERN ASIA GEOLOGICAL HAZARDS MAP: PAPER AND DIGITAL VERSIONS

increasing on the south and north sides of the old Yellow Rivermouth. Lately, human activities have become the most importantfactor in coastal erosion. For example, along the Dengzhou shoal,
the coast has disappeared completely because of the fishery industry (Guo et al.,1995).
The coast of Cambodia, which is about 435 km long, is shallow, the average depth being 50 m. Forests of mangroves and rearmangroves separate the land from the sea along sheltered coastal
sites where sufficient muddy sediments accumulate. Nearly 80%of the coastal area is still undeveloped. The absence of heavy
industrialization lessens the danger of pollution and other coastal
hazards produced by human activities (Panhasith, 1995).
Thailand has a coast line approximately 2,600 km long.
Severe coastal erosion has been caused by both natural and humanfactors. One of the most serious natural hazards is tropical
cyclones which create coastal erosion, mostly along the southeastern coast of the peninsula. The rate of coastal development, related mostly to industrial and tourism projects, during the past two
decades has been increasing and will continue to increase in the
future. This has led to conflicts over preservation of the environment vs. development. For example, the land subsidence inducedby human activities along the upper edge of the Gulf of Thailand
has led to coastal erosion in the Bangkok area (Sinsakul, 1997).
(4) Karst collapse
Karst collapse and sinkholes occur when ground water with
dissolved CO2 corrodes and erodes carbonate rocks. They, therefore, depend greatly on the geology of the area and other natural
factors such as rainfall and the occurrence of earthquakes. Karst
collapse also can be hastened by such human activities as the overwithdrawal of groundwater, mining, and reservoir construction.
Karst collapse is not shown on the printed hazard map (data is
included in the CD-Rom version) because of correlation difficulty,
so it has been summarized here for the convenience of users.
In continental China, karst collapse has occurred in 19
provinces, and 225 cities or counties. Totally 807 karst areas, 88%of which are covered with loess soil, and 45,771 sinkholes havebeen found. The Yunnan-Guizhou plateau and south China hillbasin plain karst province have been the areas most severely damaged by karst collapse. The largest sinkhole in China, in Yanguan,
Shanxi has a diameter 300m and a depth of 600 m (Institute ofHydrogeology and Engineering Geology, 1989; Wen et al., 1996).
In Thailand, highly potential karst areas are concentrated in
the southernmost part where Permian limestone predominates.
Moderate potential karst areas are found in the middle of the country where Ordovisian limestone is the dominant formation.
In Malaysia, highly potential karst areas with predominate
outcrops of limestones are present in Kuala Lumpur, Ipoh, and Bau(Ramli, 1997).
(5) Land subsidence / Ground subsidence
Land subsidence is a geological process that also may becaused by human activities such as excessive extraction of groundwater. This phenomenon has become very destructive in Asia andhas accompanied remarkable socio-economic development.
Although land subsidence is not shown on the printed hazard map(data is included in the CD-Rom version) because of difficulty incollecting data from all the concerned countries, it has been summarized here for convenience of users.
In China, a total area of 1,500 km2 is affected by land subsi-

73

dence, and thirty-seven cities, including Beijing, Shanghai, andTianjin (where 5 km2 has dropped below sea level) have suffered
severe land subsidence. The fastest subsiding region is TangguHangu in Tianjin, with a subsidence rate of about 188 mm/year.
Subsidence in that area ranged from 2.18 to 2.6 meters between
1989 and 1992 (Guo et al.,1995).
In Vietnam, land subsidence has occurred in the urban areasof Hanoi, Hochiminh City, on the Red River, and on the Mekong
Delta. Land subsidence in coastal areas results to salt water intrusion, groundwater pollution, and swamping.
In Thailand, Bangkok and its adjacent areas have been severely affected by land subsidence owing to the excessive withdrawalof groundwater. From 1987 to 1996, Bangkok sank at the averagerate of 5 to 10 cm per year, the maximum being 83.3 cm from1987 to 1992 (Ramnarong and Buapeng,1992).
In Malaysia, land subsidence caused by groundwater extraction and compaction of underlying, unconsolidated sediments also
is very common in predominantly limestone areas and in areas
developed on soft and paludal deposits (Ramli, 1997).
4. CONCLUSION
The remarkable increases in damage caused by geologicalhazards in eastern Asia in recent times are due to complicated andactive geological and tectonic settings in the region and haphazard
land-use planning and utilization in most countries in this region.
The current rapid economic development of these countries
increases the likelihood of more widespread destruction of property and the loss of human lives due to future geological hazards.
One of the most effective ways to mitigate damage caused by geological hazards is to make people better informed about the phenomena; policy makers, decision makers, politicians, educators,
and ordinary citizens. The small-scale geological hazard map is avery useful tool to better inform these people about these destructive phenomena because the paper version presents several types ofgeological hazard information in regional areas at a glance and thedigital version provides an interactive, fascinating way to handle
hazard information. We believe that these maps will become milestone contributions to hazard mitigation in Asia.
ACKNOWLEDGMENTS
We are grateful to all the people and organizations who contributed significantly to the implementation and completion of thisgeological hazard mapping project. There is not enough space tomention all of them by name. Only the contributing organizations
are mentioned: the Chinese Institute of Hydrogeology andEngineering Geology Exploration; State Seismological Bureau,
China (SSB); Geological Survey of Japan (GSJ); GeologicalResearch and Development Centre, Indonesia (GRDC);
Volcanological Survey of Indonesia (VSI); Directorate ofEnvironmental Geology, Indonesia (DEG); Korea Institute ofGeology, Mining and Minerals (KIGAM); Department of Geology
and Mines, Cambodia; Geological Survey of Malaysia;
Department of Minerals and Geoscience, Malaysia; Mines andGeoscience Bureau, Philippines, Philippine Institute ofVolcanology and Seismology (PHIVOLCS); Cavite State
University, the Philippines; Department of Mineral Resources,

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H. KATO, K. WAKITA AND J. C. BANDIBAS

Thailand (DMR); and the Geological Survey of Vietnam (GSV).
(Some names of these organizations recently have beenchanged due to reorganization)
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