About a million earthquakes shake the earth every year. The vast majority are invisible, but others highlight the power of these natural phenomena that make the world vibrate through the puzzle of the Earth’s crust: the tectonic plates.

Its discovery and study is considered one of the great scientific revolutions of the last century, and it is not surprising. Most earthquakes occur at the edges of plates, where these huge fragments of constantly moving plates touch, move apart, confront, push and hug in a passionate dance that defines the topography of the planet.

The history of plate tectonics dates back to the mid-1960s, when observations of the theory of plate tectonics revealed that the earth’s crust was divided into fragments that moved “due to the rise and fall of convection currents in the material that is under the crust something very similar to the movement of boiling cream soup”, according to the book “Geography of Mexico”.

Contemporary Spatial Mapping, edited by the Institute of Geography of the National Autonomous University of Mexico (UNAM) and coordinated by Omar Moncada and Alvaro López.

Dr. Raul Valenzuela, a researcher at UNAM’s Institute of Geophysics, also offered a conversational representation of the Earth’s crust, comparing it to the skin of an avocado, in which the mantle would be the pulp and the seed the core. The crust is a layer consisting of solid rocks between 20 and 70 km thick, while the mantle occupies 80% of the Earth’s volume, almost 3000 km thick, with varying densities and temperatures, reaching all the way to the core, which is composed mainly of iron and nickel, with temperatures of 6700 degrees Celsius.

“In geological studies, which cover the evolution of the Earth over many millions of years, the movements of tectonic plates can be observed, and with the help of GPS (Global Positioning System) methods we can measure them; however, when one plate meets another, most of the time there is no movement, but deformation at the boundary of the adjacent tectonic plate,” he explained.

Valenzuela noted that “when a large amount of strain accumulates, a rupture occurs with rapid and sudden movement that can compensate for the lack of movement due to jamming by another plate.”

so far so close

Turkey is located on the border of different tectonic plates, which, as in the case of Mexico, cause strong earthquakes with regular frequency. The 7.8-magnitude earthquake, which struck 34 kilometers west of Gaziantep on February 6 and had very strong aftershocks, has so far killed 35,000 people in Turkey and 4,000 in Syria. Another event occurred in 1999 and resulted in the death of 17,000 people.

“The occurrence of strong earthquakes in Turkey should not surprise us,” commented Valenzuela.

PHOTO: Imminent catastrophe and fear after new earthquakes in Turkey
13 Photos
Magnitude 6.4 and 5.8 earthquakes cause more structural damage and create uncertainty for citizens.

The expert also said that Turkey is submerged in its own plate, the Anatolian plate, which is small, but in the north there is a very large plate, which is the Eurasian plate, and in the south there are two other plates: the Arabian (southeast) and the African (south. -zach.).

“The latter are pressing on the Anatolian plate, and their response is to move westward. Where the Anatolian and Eurasian plates meet, there is a fault called the North Anatolian fault. Where the Arabian and Anatolian faults meet, there is another fault, the East Anatolian fault. The 1999 earthquake occurred on the North Anatolian fault, and the February 2023 earthquake occurred on the eastern fault,” he noted.

Faults are cracks in the Earth’s crust with rock blocks shifting. The boundaries of tectonic plates have large fault lines that have moved and will move throughout their history, causing earthquakes. All earthquakes are related to faults, although not all faults cause earthquakes.

“From the point of displacement, there are seismic waves that can cause destruction over great distances, even if we are not on the fault itself,” he said.

Valenzuela noted that these faults that cause earthquakes are not always at the surface, as they can be as deep as 600 km, so many of the faults will never actually be observed.

“However, there are certain regions where they can be seen, and perhaps the most obvious and infamous is the San Andreas Fault in California. In certain areas of the desert you can see where it goes, we can even measure how one block has moved relative to another over the years; in fact, the faults that cause the biggest earthquakes in Turkey are San Andreas-like faults,” he said.

overall impact

The Pacific Ring of Fire is an area where one plate subducts under another, and where the world’s most seismic and volcanic regions are concentrated. This zone releases 80% to 90% of the Earth’s annual seismic energy, but the earthquake that Turkey experienced is associated with other key seismic belts.

“The southern part of Europe and Asia are very important seismic belts. Where we find countries like Italy, Greece, Cyprus, Turkey, Iran, Pakistan, Afghanistan and India, we have the collision of the African plate with the Eurasian plate or the Indian plate with the Eurasian plate, focusing the boundary between very important tectonic plates. and with fundamental seismic activity,” he said.

There are various factors that determine whether an earthquake is more destructive than another, such as the energy released (magnitude) and the depth of the focus; the deeper it is, the less destructive it will be. Other factors are: duration, speed of seismic waves, distance to the epicenter, and soils. Also, the type of structures and materials used in buildings are decisive in the destructive nature of earthquakes.

The analysis of geodetic information that quantifies the deformation caused by earthquakes around the world is becoming more accurate thanks to satellite instruments, but it is also important to make a seismic history of all regions of the world.

“In the case of Mexico, we know very well where the edges of the tectonic plates are and where earthquakes will occur. This knowledge allows us to prepare and prevent ourselves from the future… they can be, we must have very clear building rules in the face of these realities,” he emphasized.

The IG-UNAM book mentions a comparative example of the 6.4 magnitude earthquake in India in 1993 that killed 30,000 people. By contrast, a similar magnitude 6.6 earthquake in California in 1994 caused only 55 deaths. Accidental deaths have shifted to where buildings have not been able to adapt to the type of earthquakes.

For Valenzuela, the scientific tools built around seismic knowledge should be reflected in the tools that help build cities in seismic territory.

“Turkey shows us that even with good building codes like California’s, we find ourselves in different realities, because the problem is not only good design, adequate materials and standards, but also their compliance,” he emphasized.

For the researcher, this should be a great lesson for Mexico: how far we adhere to these prerequisites. How buildings respond is the best way to prepare for the next earthquake.