Geology And Geophysics


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Earthquakes are a reminder that our planet hasn't stopped evolving. The Earth's surface, called crust or lithosphere, is made up of tectonic plates. Constant processes taking place inside and on the surface of the Earth can cause a sudden release of energy often resulting in the plates colliding with each other. That, on the other hand, can cause shaking and even displacing of the ground. Minor earthquakes (less than magnitude 4 on the scale of 1 to 10) occur all the time around the world. They aren't strong enough, to cause any damage. Stronger earthquakes are less frequent, but they take much higher toll in human life and otherwise. Here are several earthquakes, listed chronologically, that went to history as the most deadly of all times.

December 22, 856 in Damghan, Iran. It is one of the first earthquakes that have been recorded. Its magnitude is unknown. It was centered on Damghan, which at that time was one of the largest metropolis of the Middle East, and destroyed most of that city. It also caused damage to the areas stretching as far as two hundred miles east and west of the city. In mountain areas close to the center of the earthquake the surface of the ground parted in several places. Overall, 200,000 people lost their lives.

March 23, 893 in Ardabil, Iran. The death toll was 150,000; magnitude unknown. Iran has always been known as a place of earthquakes, because of its location along fault lines (large fractures of the rock formations) and on the boarder of two major tectonic plates that are always colliding. In earlier times, news of earthquakes in this remote region was almost nonexistent. The first records, dated from the seventh to tenth century, list about forty other earthquakes with estimated magnitudes ranging from 5 to 7.

October 11, 1138 in Aleppo, northern Syria. Its magnitude is unknown. The United States Geological Survey lists it as the fourth deadliest earthquake in history with the 230,000 people dead. However, the figure is based on joining of this earthquake with earthquakes in November 1137 on the Jazira plain and another one that happened on 30 September 1139 in the city of Gania, Persia.

January 23, 1556 in Shaanxi, China. It was the most deadly quake in history at magnitude about 8, killing approximately 830,000 people. More than a third of the country was affected. A 520 mile-wide area was destroyed and in some regions, 60% of the population was killed. Most of the population in that area lived in Yaodongs, artificial caves in Loess cliffs, many of which collapsed during the earthquake. The rupture occurred during the reign of the Jiajing Emperor from the Ming dynasty. That's why, in Chinese historical record, this earthquake is called the Jiajing Earthquake.

November 1, 1755 in Lisbon, Portugal. The earthquake of magnitude 9 was followed by a tsunami and fires, which caused total destruction of Lisbon and surrounding areas. Estimates place the death toll in Lisbon alone of 100,000 people, making it one of the most destructive earthquakes in history. The earthquake accentuated political tensions in Portugal and had a major impact on reducing the country's colonial expeditions. This was the first earthquake studied scientifically for its effects over a large area and eventually it led to the development of modern seismology and earthquake engineering.

December 28, 1908 in Sicily, Italy. The quake of magnitude 7.5 occurred in Messina, a city in Sicily, Italy. The Italian mainland in that area also suffered heavy damage. The ground shook for about 40 seconds, and the destruction was felt within a 188 miles radius. Moments after the earthquake, a 40 feet tsunami struck nearby coasts causing even more devastation. 100,000 residents, out of 150,000, were killed.

December 16, 1920 in Ninxia, Gansu, China. The Haiyuan or Gansu earthquake of magnitude 7.9 on the Richter scale, was followed by series of aftershocks for three years. It caused total destruction in the area. Over 73,000 people were killed in Haiyuan County. More than 30,000 people were killed in Guyuan County. Damages occurred in 7 provinces and regions, including major cities. There were large numbers of landslides and ground cracks throughout the epicentral (point on the surface of the Earth directly above the quake's origination) area. Some rivers were dammed, others changed course. Waves from this earthquake were observed even in western Norway. Total casualty was reported as 240,000.

September 1, 1923 in Kanto region, Japan. The earthquake struck the Kanto plain on the Japanese main island of Honshu. Varied records say that the duration of the earthquake was between 4 and 10 minutes. Its magnitude was 8.3 on the Richter scale and its center was deep beneath Izu Oshima Island. It devastated Tokyo, the city of Yokohama, and caused widespread damage throughout the whole region. Casualty estimates range from about 100,000 to 142,000 deaths, the latter figure including approximately 40,000 who went missing and were presumed dead.

October 5, 1948 in Ashgabat, Turkmenistan. The earthquake at 7.3 moment magnitude scale caused extreme damage in Ashgabat and nearby villages. Surface rupture was observed both northwest and southeast of Ashgabat. Death toll was said to be 110,000. A 2007 report by the State News Agency of Turkmenistan gives a total number of 176,000. The Turkmen people were just recovering from the World War II and starvation, which came right after the war in 1946-1947. The earthquake lasted only 10 seconds, but it devastated entire city. In 1995 a memorial museum was built in the middle of the city in commemoration of all the victims of the earthquake. October 5th is known as a Remembrance Day in Turkmenistan.

July 28, 1976 in Tangshan, China. The earthquake at 7.8 on the Richter magnitude scale, known as the Great Tangshan earthquake, lasted about 10 seconds and it was followed by a 7.8 magnitude aftershock 16 hours later. It is believed to be the largest earthquake of the 20th century by death toll. The epicenter of the earthquake was near Tangshan in Heibei, China. It was an industrial city with population of one million. At least 255,000 people died and another 164,000 were severely injured. The earthquake came during a series of political events involving the Communist Party of China. It shook China both literally and figuratively that year, which was later called a "Year of Curse".

December 26, 2004 off west coast of northern Sumatra, Indonesia. The earthquake, known as Indian Ocean earthquake, was caused by subduction of tectonic plates (one tectonic plate slides under another) and triggered a series of devastating tsunami along the coasts of the Indian Ocean. It killed more than 225,000 people in eleven countries, and coastal communities with waves up to 100 feet high. It was one of the deadliest natural disasters in recorded history. Indonesia, Sri Lanca, India, and Thailand were hit the hardest. With a magnitude of between 9.1 and 9.3, it is the second largest earthquake ever recorded on a seismograph. It also had the longest duration of faulting ever observed, between 8.3 and 10 minutes. It caused the entire planet to vibrate as much as 0.4 inches and triggered other earthquakes, as far away as Alaska.

October 8, 2005 in India, North West Frontier Province (NWFP), Pakistan. It is called Kashmir Earthquake, South Asian earthquake, or Great Pakistan earthquake. It was a major earthquake centered in Pakistan-administered Kashmir and in NWFP near the city of Muzaffarabad. It registered 7.6 on moment magnitude scale, making it similar in size to the 1906 San Francisco earthquake. Pakistan's official death toll was 79,000, but there were also over a thousand victims from the Indian side of Kashmir and some in Afghanistan. It is estimated that at least 86,000 died. The severity of the damage caused by the quake is attributed to severe upthrust of tectonic plates.

Since the beginning of the Earth, there have been earthquakes. Some stronger than others and some more devastating than others. It is not always the strength that decides how deadly an earthquake can be, but rather its closeness to populated areas. As the tectonic plates keep moving, the danger is always present.

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