A powerful magnitude 8.8 earthquake off Russia’s Far Eastern Kamchatka Peninsula triggered tsunami waves of up to 16 feet, which had started to American shores along Hawaii’s islands and off the coast of northern California on Wednesday morning.Tsunami alerts of varied levels have also been issued for countries such as Ecuador, Indonesia, Peru, Colombia, and Japan.Here is a look at how an earthquake can lead to a tsunami.But first, what causes an earthquake?An earthquake is an intense shaking of the ground caused by movement under the Earth’s surface. It happens when two blocks of the Earth suddenly slip past one another. This releases stored-up ‘elastic strain’ energy in the form of seismic waves, which spread through the Earth and cause the shaking of the ground.The Earth’s outermost surface, crust, is fragmented into tectonic plates. The edges of the plates are called plate boundaries, which are made up of faults — zones of fractures between two blocks of rock. The tectonic plates constantly move at a slow pace, sliding past one another and bumping into each other. As the edges of the plates are quite rough, they get stuck with one another while the rest of the plate keeps moving.Earthquake occurs when the plate has moved far enough and the edges unstick on one of the faults. The United States Geological Survey (USGS) says that “the location below the Earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the Earth is called the epicentre.”How does an earthquake lead to a tsunami?There are several factors that are involved in the generation of tsunamis.Story continues below this adLOCATION & DEPTH: The earthquake must be a marine event that displaces the sea floor. It should also be a shallow earthquake, which carries more energy when they emerge to the surface when compared to quakes that occur deeper underneath the surface. While deeper quakes spread farther as seismic waves move radially upwards to the surface, they lose energy while travelling greater distances.Shallow earthquakes generally have a depth of between zero and 70 km. In the case of the Kamchatka quake, the earthquake took place 136 km east of the coastal city of Petropavlovsk-Kamchatsky in Russia, and a shallow depth of just 19.3 km. That is one of the reasons why the earthquake was able to generate tsunami waves.TYPE OF FAULT: An earthquake that leads to tsunami generally occurs due to “reverse” faulting. In a reverse fault, the block of rock, above the fault plane, moves up relative to the block below the fault plane. This fault motion is caused by compression forces.“If big enough and close enough to the ocean floor, the energy from such an earthquake can cause the ocean floor to suddenly rise (uplift) or fall (subside). This sudden vertical displacement of the ocean floor is what typically sets a tsunami in motion,” according to a report by National Oceanic and Atmospheric Administration (NOAA).Story continues below this adAlso in Explained | Why Kamchatka in Russia is especially vulnerable to massive earthquakesThe Kamchatka quake was also a result of reverse faulting, the USGS said. It has occurred as near the Kamchatka Peninsula is the Kuril-Kamchatka Trench, a tectonic plate boundary where the Pacific Plate is being thrust beneath the Okhotsk Plate at the rate of approximately 86 mm per year. This is a relatively high speed by tectonic standards, and causes large earthquakes to happen more frequently in the region.MAGNITUDE: Tsunamis are usually generated by quakes with magnitudes of more than 7.0. However, the most destructive kind of tsunamis are typically caused by an earthquake whose magnitude exceeds 8.0. These kinds of tsunamis are capable of travelling over large distances, and lead to damage in a broader area.The Kamchatka quake had a magnitude of 8.8, and was one of the strongest earthquake since 1900.