At what intensity is there considerable damage to poorly built buildings? If you are on the first floor in a building, are you l
ikely to feel an intensity II tremor? If the pendulum of a clock in your home stops during an earthquake, at least the intensity of the earthquake in your area? During the Lisbon earthquake in 1755, a second shock wave hit. It caused The river to pull back from its banks and then the water surged forward. What intensity do you think the second shock wave was?
It is likely that the earthquake is of the magnitude of 7 on the Ritcher scale. However, other scales such as the Mercal scale are used to a less extent. The intensity of the earthquake can be characterized by the strength is has to cause shaking to the buildings and the damage is will cause. The earthquake sometimes may be felt indoors especially on the floors of the multistory buildings. This causes damage in especially poorly designed and proofed buildings.
The focus is the place inside Earth's crust where an earthquake originates. The point on the Earth's surface directly above the focus is the epicenter. When energy is released at the focus, seismic waves travel outward from that point in all directions.
