Themes
Climate
Landform &
Exogenetic
Processes
Landform &
Endogenetic
Processes
Agriculture
City
Industry
Issues
The Linear Curriculum
Climatic
Anomalies
Trouble of
Water
Natural
Hazards
Food &
Hunger
Sustainable
City
Energy
主题在各議题中的相對垂要性
議题的廣泛和跨學科性
Science
Engineering
Social sciences
Part 2. Earthquake Hazards
地震災害
Chan Lung Sang 陳龍生
Department of Earth Sciences
University of Hong Kong
Outline of Talk
Earthquake Terminology
地震學基本詞彙
Significant Earthquakes: Related
Landform & Prediction
幾次重大地震災害
Earthquake Hazard of Hong Kong
Region
香港地區地震風險
1. Earthquake Terminology
地震學詞彙
Commonly Misused Terms
• Epicenter vs. Focus (Hypocenter)
• Origin time, Travel time & Arrival time
• Seismic waves and Seismic phases
• Magnitude and Intensity
震級 (Magnitude)
• 以能量為基準，描述地震強度
• 常見震級包括黎克特制(Richter Scale, ML)
和矩震級(Moment Magnitude, MW)
• 黎克特制每級之間能量相差約32倍*
*實數為101.5
地震強度描述
描述
震級 (M)
發生頻率(每年)*
Great Earthquake
Major Earthquake
Strong Earthquake
> 8.0
7.0 - 7.9
6.0 - 6.9
1
18
~200
Moderate Earthquake
5.0 - 5.9
~2000
Light Earthquake
4.0 - 4.9
Minor Earthquake
Microearthquake
3.0 - 3.9
< 3.0
以幾何級遞增
*全球計
烈度 (Intensity)
• 以影響為基準，描述某地區受破壞程度
• 常用烈度表為修訂麥加利克度表(Modified
Mercalli Intensity Scale, MMI)
• 受震級(magnitude)、震中距(epicentral
distance)、震源深度(focal depth)、本區地質
及建築結構等影響
修訂麥加利烈度表*
I
無感(地震儀有反應)
VII
II
在樓宇上層或合適位置，
且在靜止中的人有感
VIII 行駛中汽車受到影響，若干建
築損毀 (~0.30g)
III 室內有感
站立有困難 (~0.10g)
IX
大多數人恐慌。脆弱的磚石建
築被摧毀 (~0.5g)
IV
懸掛的物件擺動
X
大多數磚石建築及木屋均連地
基摧毀。鐵軌輕微彎曲
V
室外有感
XI
鐵軌大幅度彎曲。地下管道完
全失去作用
VI
人人有感。多數人會驚慌
跑出戶外
XII
破壞幾乎是全面的
*資料來源：香港天文台
http://www.hko.gov.hk/gts/equake/mms_c.htm
烈度
VII
VIII
Site
IX
震央
Epicenter
r

震源
Hypocenter / Focus
M
Io
5 5.7
VI VII
震級M
6.3
VIII
7 7.7
IX X
VI
1556年(明世宗嘉靖35年)
陝西地震 (83萬人死亡)
海城地震：地震史上最成功一次地震預報
海城地震(M=7.3)預報時序(長．中期)
1969
1973
1974
1974.6
.12
遼寧境內斷層活動增加
地殼變形速度增快20倍
渤海水平面上升10cm
1-5月有300次小地震
預報: 渤海北部沿岸
未來一年內會有大地震
遼陽中強度地震、地形變減小、
地下水上湧、井水渾濁發泡變色
變味、動物行為異常、水氡上升
海城地震(M=7.3)預報時序(中．短期)
1975.2.1
.2.2
由.2.3.18:00
至.2.4.04:00
海城一小地震
牛群脫韁、山羊驚叫、井水上湧2米
海城七次小地震
共530次地震(最大4.7級)
.10:30
發出地震警告，疏散居民
.19:36
M=7.3 海城大地震
唐山地震：近代最大傷亡的地震
台灣地區構造
Tectonic Setting of Taiwan
921台灣地震
Taiwan Chi-Chi Earthquake
21 Sept. 1999
Mw=7.3
Deaths ~2000
車籠埔斷層．一江橋
霧峰．光復中學
卓蘭．石岡水壩
名間
Earthquake & Landform –
faullt scarp
卓蘭
Earthquake & Landform –
waterfall
Waterfalls can form in
matters of seconds
Earthquake produced landform – sand volcano
Sand volcanoes are believed to be caused
by fluidization of sand under extremely high
pore pressure
名間
Induced landslips
堰塞湖 (quake-dammed lake)
3. Earthquake Hazard of Hong
Kong Region
香港地區地震風險
Seismic Hazard (災害)
& Seismic Risk (風險)
• Seismic Hazard: 發生某一強度地震的
機率
• Seismic Risk: 地震的潛在損失
地震災害
Earthquake Effects
Primary effects
Secondary effects
•Ground shaking
•Surface rupture
•Ground failure
•Tsunamis
•Fire
•Floods
•Landslips
•Epidemics
Tertiary effects
•Loss of work day
•Long term psychological damage
•Long term medical cost
中國各類自然災害死亡人數比較
1949－1995
氣象災害
地震災害
地質災害
其他災害 (1%)
海洋／森林災害 (1%)
1918年汕頭地震(M=7.25)
(香港有紀錄以來唯一一次導致建築物損毀的地震)
Ground Shaking Estimation 地震动估计
•
Deterministic 確定性方法
1.
2.
3.
•
Select scenario earthquake event – a ‘design’ earthquake.
Determine attenuated bedrock ground motion at site.
Modify motion for local geology.
Probabilistic 概率性方法
1.
2.
3.
4.
Identify all possible earthquake sources.
Model occurrence of events.
Determine attenuated bedrock motion at site.
Integrate effects of all events to determine maximum credible
intensity.
Magnitude-Frequency Relation
Log N = a + b M
N : Cumulative frequency
M: Magnitude
a depends on seismic intensity
b is ~ -1.0
Earthquake Recurrence
return period = 1/N
N = 10/y
N = 0.1/y
r.p. = 36 days
r.p. = 10 years
N: number of earthquakes greater than a
certain magnitude
a and b determined from earthquake records
Earthquake Magnitude - Frequency
Relation for Mainland China (19701990)
Return period
M=4 N=414/y
t = 0.9 day
M=5 N=67/y
t = 6.3 days
M=6 N=11/y
t = 0.1 year
M=7 N=1.8/y
t = 0.6 year
Department of Earth Sciences, HKU
http://www.hku.hk/earthsci
m
Annual occurrence rate and return period of earthquakes
in Southern Coastal Seismic Belt (Chan et al, 1997)
Magnitude
onshore region
offshore region
events/yr
period(yr)
4.0
1.05
0.95
1.38
0.72
4.5
0.44
2.29
0.65
1.55
0.18
5.59
0.30
3.33
5.5
0.07
13.6
0.14
5.15
6.6
0.03
33.2
0.06
15.3
5.0
events/yr
period(yr)
Teaching of Earthquake Hazards
•
•
•
•
•
•
Relation of earthquake & plate tectonics
Basic seismic terms
Earthquake effects & landform
Basis for hazard & risk estimates
Risk & economy
Awareness and preparedness
Thank You!
chanls@hku.hk
Department of Earth Sciences,
University of Hong Kong