Earthquakes and Their Dangers Earthquakes

Earthquakes and Their Dangers

Earthquakes have always been feared for their catastrophic effects and strike without much of a warning. Many recent earthquakes such as the El Salvador quake and the one that happened in India in 2001, and more recently the earthquake in Indian Ocean that triggered the devastating tsunami in Asia, have all proved that major earthquakes tend to be unpredictable in spite of the advanced scientific equipments used by seismologists. Though scientists now have knowledge about seismic faults and can predict where the next earthquake could occur they do not yet possess the knowledge to predict when the next 'big one will strike" [Sandra Blakeslee] Let us have a brief overview of three major earthquakes of the last century, namely, the 1976 Tangshan earthquake in China, the 1982 New Brunswick quake, and the 1906 quake of San Francisco so that we would get a better idea of the intensity of the damage and how well the situation was handled.

Tangshan China 1976

The 1976, July 28th quake that shattered the Chinese industrial city of Tangshan is considered to date as one of the most devastating earthquakes to have occurred during the last four centuries. The disaster struck in the very early hours of the day at 3:42 A.M when most of the residents were peacefully sleeping. Though the Chinese government was pretty closed and unwilling to reveal data pertaining to human casualties immediately, reports, mainly from western journalists started emerging very soon and the death toll was put at 7,50,000 people in and around the city of Tangshan which happened to be the epicentre. The Tangshan earthquake is estimated to be between the range of 7.8 and 8.2 on the Richter scale, which explains the intensity and the large-scale destruction. Reports indicate that a whole area, four miles long and five miles wide, along the heart of the densely populated city was decimated and for 40 miles on either side of the city villages were destroyed. [Reuters] People who happened to survive the quake reported it as 'a huge jolt from below' and that the factories and other big housing structures instantly collapsed 'as if they were made of cards'. [Andrew H. Malcolm] Aftershocks continued to rock the city for over a year after the quake. The Chinese military undertook the relief measures in full swing and medical teams (called barefoot doctors) operated in Peeking to take care of the refugees from Tangshan. The Chinese premier Hua kuofeng himself toured the affected regions and supervised the relief operations. [New York Times]

Though in some instances as the Lungling and the Haicheng earthquakes the Chinese were able to give imminent prediction (successfully) they were not able to give such a short-term prediction in the case of the Tangshan quake. (Though midterm prediction was issued in January). However, it must be noted that Wang Chengmin, a scientist representing the State Seismological Bureau of north China forewarned the possibility of an earthquake in the Tangshan region. In his words at a conference conducted on July 16, 1976, Wang had said ' There is a strong possibility of a magnitude 5 earthquake from July 22 to August 5, 1976 in the Tangshan region. A magnitude 8 is also likely in the second half of '76. Preparations should be made immediately" [Globalwatch]. The Qinglong country, which acted upon the advice, had no human causality (only one due to heart attack) during the earthquake while in Tangshan a staggering 2,40,000 people were killed immediately.

The San Francisco Earthquake-1906

The Apr 18, 1906 San Francisco earthquake is considered as one of the most intense earthquakes in the American continent during the last century. The foreshocks were experienced very early in the morning, at around 5:12 AM, which was immediately followed by the main quake. The quake intensity as per the Mercalli scale that was used at that time was between 8 and 9, which seismologists today equate to a value of 7.9 on the Richter scale. [Dr. Frank J. Collazo] the quake created a rupture of 296 miles, which rates it as one of the biggest quakes ever. Geologist John M. Clarke said, " the heavy waves travelled at the rate of about 11,000 ft a second and the lighter preliminary and subsequent waves much more rapidly, at about 40,000 feet a second." [New York Times]

With San Francisco as its epicentre, the quake took a toll of 3000 human lives and absolutely wrecked the city destroying most structures while what was left was consumed by the conflagration that ensued. The predominantly wooden structures of San Francisco was the reason for such a rapid spread of fire. [New York Times] in an attempt to stop the spreading fire firelighters were forced to destroy buildings on its path by dynamiting. Water shortage made things worse for the fire fighters who tried their best to douse off the fury of the flames. The quake triggered a new interest in the study of earthquakes, particularly in the study of the San Andreas fault line and contributed immensely to the scientific research on earthquakes. Mr. Henry Fielding Reid, a Geology professor at the Johns Hopkins University and one of the researchers involved in the study of the 1906 quake, proposed the 'elastic rebound theory' which even today constitutes the base of our understanding of earthquakes. [USGS]