Nepal Earthquake – The Numbers

The Wall Street Journal

59分鐘 · 

There have been 31 aftershocks in Nepal since Saturday's earthquake.

A look at the disaster by the numbers.

參考翻譯

Nepal Earthquake – The Numbers

The massive earthquake that shook Nepal on Saturday has so far claimed the lives of at least 1,900 people. Here's a look at the temblor by the numbers.

BLOGS.WSJ.COM

THE NUMBERS

Nepal Earthquake

2:14 AM EST APR 26, 2015

By 

Joanna Sugden 

and 

Sean McLain

CONNECT

SHARE 

 

 

 

The massive earthquake that shook Nepal on Saturday has so far claimed the lives of at least 1,900 people.

The quake, which struck shortly before noon, local time, spread devastation across a broad swath of territory, severely damaging parts of the capital’s historic center, flattening remote villages and triggering a deadly avalanche on Mount Everest.

Here’s a look at the earthquake by the numbers.

Source: U.S. Geographical Survey and WSJ reporting. 

• 7.8

  The earthquake that hit Nepal on Saturday was magnitude 7.8.

  Magnitudes are calculated from the ground motion recorded on seismographs.

  The scale is designed such that an earthquake of magnitude 8.0 produces a seismic wave 10 times larger and releases 31 times more energy than that of an earthquake with a magnitude of 7.0, for example.

• 9.3

  The epicenter was 9.3 miles underground. Earthquake up to 43 miles below the surface are described as shallow. Earthquakes occur in the Earth’s crust or upper mantle. They can be as much as 500 miles deep.

  The shallower the earthquake, the greater the shaking above ground. 

  Geologists determine the depth of an earthquake using seismograms.

  Primary or P-waves – the first to reach a seismic station after an earthquake — travel at a speed usually less than 3.7 miles a second in the Earth’s crust and jump to 8 miles a second through the core.

  Secondary, or S-waves, are the second waves recorded and travel at a little over half the speed of the P-waves. The time difference between the P- and S-waves arriving at several seismograph stations is used to locate the origin of the earthquake. 

• 31

  There were 31 aftershocks recorded in Nepal during the 23 hours after the 7.8-magnitude quake on Saturday morning. All of them were magnitude 4 and above.

• 328

  A 328-yard layer of black clay beneath the Katmandu Valley, the remnants of a prehistoric lake, amplifies the damage caused by earthquakes, according to a 2004 study by the Netherlands-based International Institute for Geo-information Science and Earth Observation. As a result, the region is prone to soil liquefaction in strong earthquakes, when vibrations can cause solid ground to turn in to something akin to quicksand, swallowing buildings.

• 2.5 Million

  Number of people living in Katmandu and the surrounding valley.

• 8.6

  The largest instrumentally recorded Himalayan earthquake, which occurred Aug. 15, 1950, in Assam in eastern India, was magnitude 8.6. It was felt across much of central Asia, causing extensive damage to villages in the region above the epicenter, according to the U.S. geographical survey.