The Institute of Geophysics explains the earthquake miscalculation in Phu Yen

Dr. Le Huy Minh, Director of the Earthquake Alert and Tsunami Warning Center and Assoc. Prof. Dr. Nguyen Hong Phuong, Deputy Director of the Earthquake Reporting Center and tsunami warning had an analysis to explain the calculation. wrong earthquake on August 25, 2011 in East Sea, about 300km from Phu Yen coast

>>>Warning earthquake due to positioning software
>>> Earthquake about 300km from Phu Yen coast

The article is published on the website of the Institute of Geophysics (Vietnam Academy of Science and Technology).

According to the article, from May 2009, within the framework of cooperation between the Institute of Geophysics and New Zealand Institute of Geology and Nuclear, Seiscomp 3 software was installed on the computer system at the Earthquake Reporting Center and tsunami warnings that allow real-time seismic data collection of large seismic stations in Vietnam (currently 12 stations) and in Southeast Asia (more than 20 stations).

This is a software developed by the Institute of Geophysics Posdam, the Federal Republic of Germany, which is the most advanced type in collecting, managing and processing earthquake data.Seiscomp 3 software allows to determine earthquake parameters automatically (seismic coordinates, damping depth, magnitude) with good accuracy when earthquakes occur in Vietnam and neighboring areas by usage of next time wave P is transmitted directly from earthquake source to observation stations (this software is being used in seismic data processing centers and early warning of tsunami of Indonesia, Thailand, Malaysia, Philippines .).

The earthquake on August 25, 2011 was determined by the data obtained from the wide-range seismic station system and Seiscomp 3 software which occurred in the area between the East Sea and magnitude is M = 5.4. Actual initial calculation thanks to Seiscomp 3 software, the depth of absorption is 250km. However, this depth is not suitable for the actual earthquake activity in the East Sea region, because here the crust thickness is only about 10 km; Large-scale earthquakes usually appear only in submerged areas.

Seiscomp 3 software does not distinguish these waveforms from direct to vertical waveforms, resulting in incorrect positioning of the earthquake source.

This is the first time the Earthquake Reporting Center and tsunami warnings have received information about such an earthquake.

Based on the velocity models in the Earth's layers, it can be deduced that the P waves passing through the Earth's core take about 20 minutes, referring to the earthquake catalog of the US Geological Department, Dr. Le Huy. Minh said that the August 25 earthquake announced that it could be the earthquake in the western hemisphere with the following parameters: the time of the earthquake was 17: 46 minutes 11 seconds GMT on August 24, News 0 hours 46 minutes 11 seconds Hanoi Hanoi on August 25, the center coordinates: 7,644 ^o S, 74,506 ^o W (northern Peru), the depth of the target: 145.1km, magnitude 7.0 the Richter scale.

However, to correct this, it is necessary to solve the seismic wave transmission problem from the earthquake source which mentioned the location of earthquake observation stations in Vietnam and neighboring areas with the selection of structural parameters The structure of the Earth is reasonable, this is a problem that is not simple, requiring information from many fields of studying the science of the Earth (such a series of earthquake-transmitted data like that has been many scientists. International use for the study of the internal structure of the Earth's core.

Photograph of the East Sea region from the earthquake satellites on August 25

Illustration of the propagation of seismic waves in the Earth and the existence of dark seismic waves created by the Earth's core.Vertical P waves emitted by an earthquake occurring at point F can be transmitted directly to all points at the Earth's surface with angular distance from F less than 105 ^o .

Due to the existence of the liquid nucleus, and the refraction of seismic waves when propagating in the nucleus, P waves cannot reach the area at 105 ^° to 142 ^o (dark) angular distance, which can be understood as a The simple way is as follows: Vertical waves from earthquake source F slip through the nucleus surface and emerge on the ground at point P; a wave with an angle of incidence greater than the incident angle of the beam ray at P (with a very small value) will be refracted in the nucleus with the rays on the ground numbered as 1; the angle of incidence of the incident wave continues to increase, the ray pounces backward at point 2, the angle of incidence increases to a certain value, the ray will reach the point at a distance of 142 ^o and is numbered 3, the angle of incidence increases. moreover, the rays appear larger corner angles and numbered 4.

So for every angle of incidence, longitudinal waves of P cannot appear in the dark, and longitudinal waves traveling through the Earth's core appear at an angle of greater than 142 ^° from the earthquake source location.

Talking to reporters, Dr. Le Huy Minh said, errors in the process of calculating earthquakes are entirely possible. Although it has not caused serious consequences, the Center has promptly detected and informed accurately and withdraws experience. This is a lesson for the Center to report earthquakes and tsunami warnings later. This is the last information about this earthquake.

As PV reported, on August 25, the Earth Physics Institute issued a notice, when 1 hour 3 minutes on August 25 (18:03 GMT) occurred a magnitude 5.1 earthquake. It is located at the position of coordinates 13 degrees 41 'north latitude, 112 degrees 22' east longitude and depth of about 250km.

However, after finding a mistake, the Geophysical Institute was promptly informed again. This earthquake strengthened 5.4 Richter scale at the position of coordinates 13 degrees 12 'north latitude, 112 degrees 95' east longitude and the depth of shock was only about 15km.