潘亚农

（巢湖学院物理系，安徽 巢湖 238000）

陆域地震的前兆现象

潘亚农

（巢湖学院物理系，安徽 巢湖 238000）

地震是人类目前还难以控制的自然灾害.但在多数剧烈的陆域地震发生以前，伴随地下岩层中应力和应变能的积累，在相关的区域可能出现一些地震前兆，例如地面倾斜、前震、地电和地下水异常、动物行为异常等.因此，研究前兆现象与未来地震之间的内在联系，有助于防震减灾工作.

陆域地震；前兆现象；动物行为异常

Earthquakes are a geological phenomenon.They are a hazard that humans live with but cannot control.But severe continental earthquakes seldom strike without forewarning. Various precursory phenomena（clear or subtle）often occur before large continental earthquakes.Some of these earthquake precursors are widely known in East Asia.

1

Due to crustal deformation and gradual tilting of the land prior to large earthquakes,the elevation of some bench marks in the affected area will change.These changes can be detected by precise levelling and used to estimate the tectonic strain built up in the subsurface rock layers and the potential seismic activities in the future.Geoscientists in Japan and China have used this method to make long-term earthquake predictions.

2

The change of geoelectric potential difference in the affected area often becomes increasingly active and noticeable before an approaching earthquake.When l participated in earthquake precursor observation work in Anhui Province, P.R.China in 1976,l witnessed this distinctive precursory phenomenon with my own eyes.After l reported this distinctive event to a local government,a small earthquake occurred in a neighboring county（Dingyuan County） the following day.Very active geoelectric changes also occurred just before the 1975 Haicheng earthquake and the 1976 Tangshan earthquake.Active changes in geoelectricity are a fairly clear forewarning.As a result, this king of geoelectricity observation methods were widely used in many Chinese middle school laboratories in the 1970s.

3

Due to crustal strain，groundwater in the affected area may change itswater level，flow rate，transparency，color，taste or smell before a severe earthquake.For example,a study shows that the residents in 48 counties around Tangshan had noticed 868 macroscopic hydrologic anomalies before the 1976 Tangshan earthquake.And so a Chinese rhyme goes:“Groundwater is a precious thing， the earthquake precursors come early.”

4

Repeated small earthquakes，unusual change of sea level，strange weather conditions and ionospheric changes have been predictors of an approaching large earthquake. For example，the changeofnearby sea levelbeforethe 1975 Haicheng earthquake， the severe drought in the Songpan—Longmenshan area before the 1976 Songpan—Pingwu earthquake, the unusual hot weather just before the 1976 Tangshan earthquake，the distinctive cloud formations and widespread apparentionospheric changes before the 2008 Wenchuan earthquake.Some scientists in China mainland and Taiwan have mentioned these ionospheric changes.

5

Some animals often change their behavior patterns before devastating earthquakes.For example,hibernating snakes came out in cold winter，welltrained police dogs whined at night before the Haicheng earthquake,thousands of animals became nervous before Tangshan earthquake,mass migration of toads occurred in Mianzhu three days before the Wenchuan earthquake.

A well－known Chinese rhyme appeared in lots of propaganda posters put up by inland local governments in the 1970s was most significant and enlightening.It was a very vivid summary reflecting Chinese people′s real experiences and understanding.It mentioned the erratic behavior in 16 kinds of animals before severe earthquakes.This is an English translation of that Chinese rhyme:

Erratic animal behavior will occur before severe earthquakes.

It is most important for us to watch them carefully.

Mule,horse,cow and sheep refuse to go back into fold.

Mice flee away in groups even in the daytime.

Chickens fly onto trees and pigs try to escape from sty.

Ducks and geese fear water and dogs whine.

Hibernating snakes come out in winter.

Swallows,pigeons and birds fly away and never return.

Rabbits erect their ears upright and tremble in terror.

Frightened fish stay motionless on surface of water.

Everyone in every family should watch out for them,

And report the anomalies to the government without delay.

We can also have a Iook at that Chinese rhyme in square characters:

震前动物有前兆，密切监视最重要.

骡马牛羊不进圈，老鼠成群往外逃.

鸡飞上树猪拱圈，鸭鹅怕水狗哀嚎.

冬眠老蛇早出洞，燕雀家鸽不回巢.

兔子竖耳跳又撞，游鱼惊慌水面漂.

家家户户细观察，综合异常早汇报.

As there have been various cases of unusual animal behavior before most large earthquakes,especially in the 24 hours before them,many experienced observers and local people believe that the number of fatalities and injuries could have been much smaller if the public in disaster areas had been conscious of this significant precursory phenomenon.

6

Historical records of past earthquakes show that terrible underground thunderous sounds,mysterious lights and flashes often occur just before large earthquakes.People should be evacuated from unsafe buildings as quickly as possible when these warning signs occur.

In actual fact,most continental earthquakes in Asia occur in the crust at depths of less than 40 km.Along with the rupture-generating crustal deformation,various precursory phenomena（clear or subtle）often occur before large continental earthquakes.Experienced observers seldom miss these precursory phenomena.Although at the present time the scientists can only find out some fuzzy information about a silently approaching potentially damaging earthquake,this kind of forewarning is quite usefu.It enables local governments and the public to be aware of the possible danger and make arrangements beforehand.

Chinese scientists have drafted and published various seismic design codes since the 1970s.but some builders and related functionaries often ignore the essential instructions in the building codes.To strengthen all the unsafe houses and school buildings in a short period is quite impossible.Moreover,unscrupulous builders may build shoddy houses in the future.And these houses may cause trouble.So we must support researches on the likelihood of future earthquakes.Even though earthquakes can not be predicted with a hundred percent certainty, there are many well-founded empirical methods that we can use to help predict large earthquakes.Forewarned is forearmed.For some practical purposes（e.g.forewarning of potentially damaging earthquakes,making arrangements in advance and minimizing casualties）,earthquake prediction is necessary and useful.

PRECURSORY PHENOMENA OF CONTINENTAL EARTHQUAKES

PAN Ya-nong
（Department of physics,Chaohu University,Chahu Anhui 238000）

Earthquakes are a hazard that humans cannot control.But before severe continental earthguakes,as stress and strain energy accumulate in the subsurface rock layers,various earthguake precursors（gradual tilting of land,foreshock,geoelectricity and groundwater changes,erratic animal behavior）may occur in the affected area.Consequently,researches on the inherent connection between precursory phenomena and potential seismic activities in the future are beneficial.

Continental earthquakes;Precursory phenomena;Erratic animal behavior

X43

A

1672－2868（2011）06－0060－03

2011-11-30

潘亚农（1935-），男，湖南湘乡人。巢湖学院物理系，副教授

责任编辑：宏 彬