• A powerful earthquake rattled Myanmar and neighbouring Thailand, trapping dozens of workers in a collapsed under-construction skyscraper in Bangkok where a state of emergency was declared on March 28.

• The earthquake struck central Myanmar, and several buildings collapsed in Mandalay, the country’s second-largest city. 

• The United States Geological Survey (USGS) said the quake was of 7.7 magnitude and at a depth of 10 km. It was followed by a powerful aftershock.

• The epicentre was about 17.2 km from the city of Mandalay, which has a population of about 1.5 million.

• While the area is prone to earthquakes, it is generally sparsely populated and most houses are low-rise structures.

• The quake forced the suspension of some metro and light rail services in Bangkok, where Thai Prime Minister Paetongtarn Shinawatra declared a state of emergency.

• Tremors were also felt in China’s southwest Yunnan province.

What is shallow earthquake?

Earthquakes can occur anywhere between the Earth’s surface and about 700 kilometers below the surface. For scientific purposes, this earthquake depth range of 0-700 km is divided into three zones: shallow, intermediate and deep.

i) Shallow earthquakes are between 0 and 70 km deep.

ii) Intermediate earthquakes 70-300 km deep

iii) Deep earthquakes 300-700 km deep. 

In general, the term “deep-focus earthquakes” is applied to earthquakes deeper than 70 km.

Some terms related to earthquake

Earthquake: An earthquake is a sudden, rapid shaking of the ground caused by the shifting of rocks deep underneath the earth’s surface. Earthquakes can cause fires, tsunamis, landslides or avalanches. Earthquakes are classified as, Slight (M<5.0), Moderate (5.0<M<6.9) and Great (M>7.0) depending upon the magnitude on the Richter scale. An earthquake having a magnitude, M<2.0 is termed as a microearthquake. 

Seismograph: A seismograph, or seismometer, is an instrument used to detect and record earthquakes. Generally, it consists of a mass attached to a fixed base. During an earthquake, the base moves and the mass does not. The motion of the base with respect to the mass is commonly transformed into an electrical voltage. The electrical voltage is recorded on paper, magnetic tape, or another recording medium. This record is proportional to the motion of the seismometer mass relative to the earth, but it can be mathematically converted to a record of the absolute motion of the ground. Seismograph generally refers to the seismometer and its recording device as a single unit.

Richter scale: The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude 5.3 might be computed for a moderate earthquake. 

Epicenter: It is the point on the surface of the Earth, vertically above the place of origin (hypocenter or focus) of an earthquake.

Aftershock: An earthquake that follows a large magnitude earthquake called, “main shock” and originates in or around the rupture zone of the main shock. Generally, major earthquakes are followed by a number of aftershocks, which show a decreasing trend in magnitude and frequency with time.

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