I live in Lima , Peru , and on Wednesday we just had the strongest earthquake in decades . The towns south of Lima were the most affected due to poor structures and materials used in homes and different buildings , killing about 500 people as of today and leaving about 150,000 homeless . The thing is that the whole country is shivering , we had over 400 aftershocks so far , so I wonder how it is that the whole country is shivering ?
The Earth has a crust that appears to be solid, but it is actually made up of plates that are constantly slowly moving a round. If there movements are under a lot of pressure they finally shift with tremendous force causing the Earth to shift so abruptly that earthquakes are created. The most dangerous plates are usually found around the Pacific Rim and where mountains are being formed by the upheaval of the Earth's plates. Think of the Earth as a giant jigsaw puzzle. All of the sudden the pieces start moving around like when you are looking for the right piece. Finally, you find that piece and you try to fit in, but in reality it isn't the right piece so you try harder to make it fit and as you do so all the pieces of the puzzle are affected. Those closest to what you are doing are the most affected and their sides are pushed up or down, or both. That is the best analogy I can come up with. The edges pf these plates are called fault lines and are the weakest.
Want to know why all of Peru is shaking after the big quake? Earthquake waves work the same way sound waves work. How is it that you can sometimes hear somebody speaking when he/she is on the other side of the room? Because the voice of that person puts pulses into the air that spread out in all directions at the "speed of sound", and when those pulses arrive at your ear, you hear their voice. Earthquake waves are a similar concept. The tectonic plates that are constantly in motion grinding and bumping each other want to shift, but rock deep in the earth's crust locks up and prevents the movement. Eventually (...often several hundreds of years), enough pressure builds up that the rock that was locked up breaks, thus releasing a huge amount of energy and allowing the tectonic plates to move. This energy pulse that is released travels out in all directions from where the rock broke (i.e. the "hypocenter"), traveling through the rock and soil of the earth. As the waves spread out, they eventually begin to be damped, filtered, and overall diminished. That's why people don't physically feel the Peru earthquake up in the United States. But you guys down in Peru are close enough to the hypocenters of the quakes to feel the shaking.
You might want to know what aftershocks are. Aftershocks result from the distribution of stress from where it used to be isolated (i.e. at the location of the hypocenter), but was distributed to surrounding rock once the earthquake occurred. Usually, small quakes will occur as this stress is distributed and the earth is trying to acieve equilibrium.