To understand the following article, before, it is necessary to share with you a brief explanation about tectonic plates, which is a relatively rigid fragment of the earth’s crust (lithosphere) that moves over a relatively plastic zone of the upper mantle of the Earth’s layer.
The tectonic plates that affect Costa Rica are the “Caribbean” and the “Coco” plates. The Coco plate sinks (subsumes) under the Caribbean plate and during this process is that most of the earthquakes that affect us are generated. Besides, the Deformed Belt of Northern Panama (CDNP) is distinguished, a system associated with the fault that originated the Limón earthquake in 1991.
The Panama Fracture Zone (ZFP) is a fault system with a large north-south direction. seismic activity. The plate of the Coco will affect the seismic behavior because the energy tends to concentrate around the submarine “mounds” as the Coco plate sinks under our country, the pressure increases, producing a sudden movement, called an earthquake. The plate of the Coco will affect the seismic behavior because the energy tends to concentrate around the submarine “mounds”.
So what is a fault?
Faults are cracks in the lithosphere, along which the movement has taken place, thus displacing blocks on both sides. The origin of this movement is tectonic forces in the earth’s crust, which cause breaks in the earth’s crust.
These zones store energy for a more or less prolonged period, deforming until the moment comes when the forces of both blocs are so great
that end up moving suddenly. When this happens, seismic waves are generated that propagate in all directions, producing earthquakes. Therefore, where these faults or tectonic plates (with the epicenter of terrestrial malformations) collide, they produce seismic movements that can cause an earthquake or tremors of varying magnitude and changing the terrestrial morphology (form).
There are 3 types of faults.
Normal. This type of fault is characterized by one of its blocks (upper) falling under the action of gravity, and the tectonic forces act by dilating or expanding the area perpendicular to the fault.
This type of fault is characterized by the fact that one of its blocks (upper) is pushed upwards due to the compression forces acting on the crust. The tectonic forces act by compressing the area perpendicular to the fault. The Limón earthquake that took place in 1991 was caused by this type of fault. The coast rising of approximately one meter that is observed today was since the block of the fault that was built corresponded to the side where the Costa Rican territory is located.
This is the type that occurs when the tectonic forces act in the opposite direction on both sides of the fault and parallel too between them. As a consequence, the blocks are displaced horizontally.
Throughout all these types of faults are areas that have a higher concentration of energy than others, the hypocenter being the point where the rupture begins and from which the waves propagate, but this is not necessarily the point from where the greatest amount of energy is radiated from an earthquake.
When an earthquake occurs, seismic waves propagate in all directions starting from the hypocentre. Not all types of waves are the same, as there are important differences among them, the waves always appear registered in the seismograms. The superficial waves only appear in those registers of earthquakes whose hypocenter has not been very deep.
Earthquakes originate at a certain depth at a point called hypocenter. From there, seismic waves propagate in all directions. The point projected on the surface, directly above the hypocentre, is called the epicenter, that is, the place from where it radiates seismic waves to adjacent areas. A fault scarp is a rupture produced by the surface fault, but it does not always occur. Faults that do not break the surface when an earthquake occurs are called blind faults and are perhaps the most dangerous because there are no visual samples of their existence. If this type of fault exists, the citizenry must be informed to be very alert since it generates more danger due to its rupture under the earth’s crust although not visible.