Earthquakes in China

Introduction

China is located in one of the most active seismic regions of the world and has been plagued by numerous destructive earthquakes during its long history. The most significant of these earthquakes, in terms of lives lost, was that which occurred in 1556. In the last twenty years China has experienced the second most destructive earthquake in its history. The following is a brief account of the 1556 and the recent 1975 and 1976 earthquakes.

The Great China Earthquake of 1556

The worse natural disaster in recorded history, at least in terms of lives lost, was caused by an earthquake in Hausien in the Shensi Province of China in 1556. The earthquake devastated 98 counties and eight provinces of Central China. The destruction spanned an area of 500 miles, and in some counties the average death toll was 60 percent of the population. A total of 830,000 people lost their lives, most of them from the collapse of poorly constructed houses. The magnitude of this earthquake has been estimated to be from 8.0 to 8.3 on the Richter scale.

The Haicheng Earthquake of February 4, 1975

On February 4, 1975, Haicheng, a town with about 100,000 inhabitants in the Liaoning Province of northeast China, was struck by a 7.3 magnitude earthquake. As early as 1970, the State Seismological Bureau, had identified the Liaoning Province as an area of high earthquake risk. Based on studies of precursor events and unusual animal behavior, a warning was issued by local authorities. Thus, when the earthquake struck on February 4, there were few lives lost as most inhabitants had evacuated to safer places. However property damage was high.

The China Earthquake of July 28, 1976 (The Tangshan Earthquake)

No other earthquake in this century has been as catastrophic or has claimed as many lives as the great earthquake that struck the city of Tangshan, in Northern China, on July 28, 1976. Tangshan, a thriving industrial city with one million inhabitants, is located only about 95 miles east, and slightly south, of Beijing. Although the region had experienced moderate seismic activity in the past, the city of Tangshan has been built on unstable, alluvial soil. To make matters worse, The city is located in the center of an area with major crustal faults on four sides. Furthermore, a 25-mile long fault passes through Tangshan, where only few of its structures are earthquake-resistant.

In the early morning hours of July 28, while the city was asleep, the magnitude 8.0 earthquake with its epicenter right on the city broke a five-mile section of the fault. Along the west side of the fault the land moved five feet northward in relation to the land on the east side. The east block tipped downward at the northern end of the break, and upward toward the south end. Over a four-by-five mile area the devastation of the city was nearly total. The force of the quake motions were so strong that people reported being thrown in the air. Within seconds, thousands died. Property destruction was unbelievable. Bridges, railroads, homes, factories were completely leveled. In the harbor city of Tientsin, 60 miles to the southwest, and in Beijing to the west, the quake jolts forced thousands of frightened people into the streets seeking refuge from aftershocks.

導(dǎo)言

中國是世界上地震最活躍的地區(qū)之一，在其悠久的歷史中，曾遭受了許多破壞性的大地震。就人員傷亡而言，1556年發(fā)生的大地震損失最為慘重。在過去的二十年里，中國還經(jīng)歷了另一個最破壞性的大地震。以下是簡1556以及最近的1975年和1976年的特大地震的簡單介紹。

1556年特大地震

就傷亡人數(shù)來說，有記載最嚴重的自然災(zāi)害，是1556年發(fā)生在陜西華縣的超強地震，那次地震共摧毀了中國中部地區(qū)的8個省和98個縣。破壞范圍面積達500英里，因為房屋簡陋，83萬人失去了生命。在一些受災(zāi)縣，平均死亡人數(shù)為60 %。據(jù)估計，這次地震為里氏8.0到8.3級。

1975年2月4日海城地震

1975年2月4日，在中國東北遼寧省的海城，一個約有十萬居民的鎮(zhèn)，發(fā)生了7.3級的特大地震。早在1970年，國家地震局就把遼寧省確定為地震高風(fēng)險地區(qū)。當(dāng)?shù)卣鶕?jù)震前先兆與動物的反常行為，發(fā)出了地震預(yù)警。當(dāng)二月四日爆發(fā)大地震時，因為大部分的居民已疏散到安全的地帶，生命損失很少。不過財產(chǎn)損壞很大。

1976年7月28日特大地震(唐山大地震)

在本世紀，沒有任何其他大地震能與發(fā)生在1976年7月28日中國北方的唐山市所造成的巨大災(zāi)難或死亡人數(shù)相比的特大地震。唐山位于北京東部偏南95英里(原文如此，譯者注)，人口一百萬，是一個繁榮的工業(yè)城市。過去該地區(qū)曾經(jīng)歷過中度地震活動，唐山市的地基不穩(wěn)定，土壤為沖積土質(zhì)。更為糟糕的是，唐山正好處于四周為主要的地殼斷層的區(qū)域中心。此外， 25英里長的斷層帶正好通過唐山，唐山的建筑物結(jié)構(gòu)很少具有抗震性。

7月28日清晨，整個城市還在睡夢中，突然爆發(fā)了8.0級特大地震，震中在斷層的5英里處，正好是唐山市的中心位置。與東側(cè)相對而言，沿著斷層的西側(cè)整個土地向北移動了5英尺。在裂縫處北端東部，地塊北向下傾斜，南邊翹起。整個唐山幾乎全部夷為平地。有報道說，地震的威力之強大把人都拋到了空中。頃刻間，數(shù)千人喪失了生命。財產(chǎn)的損失更是難以置信。橋梁、鐵路、房屋、工廠完全夷為平地。在西南60英里以外的港口城市天津，及西面的北京，大地震動迫使數(shù)以千計受到驚嚇的老百姓在后來的多次余震中露宿街頭尋求安全。