Types of seismic waves created by an earthquake include P-waves and S-waves that travel throught the earth as well as surface waves, which can cause a lot of damage at the Earth's surface.
Courtesy of USGS
Seismic Waves: Moving and Shaking During an Earthquake
During an earthquake, energy is released in seismic waves that travel from where the earthquake starts, a place called the focus. The seismic waves radiate from the focus. Seismic waves cause intense shaking at the Earth surface that can cause buildings and roads to collapse.
Police Lieutenant H.N. Powell described his experience witnessing the impact of the seismic waves of the 1906 San Francisco, CA earthquake like this:
"Valencia Street not only began to dance and rear and roll in waves like a rough sea in a squall; but it sank in places and then vomited up its car tracks and the tunnels that carried the cables. These lifted themselves out of the pavement, then bent and snapped. It was impossible for a man to stand, or to realize just where he was trying to keep standing. Houses were cracking and bending and breaking the same as the street itself and the car tracks."
Not all seismic waves as the same. There are several different types and each type has a unique way of moving. Accounts of what it was like to be in an earthquake usually describe surface waves since those are most noticeable at the Earth's surface.
Surface waves travel over the Earth's surface.
- Rayleigh waves, also called ground roll, travel like ocean waves over the surface of the Earth, moving the ground surface up and down. They cause most of the shaking at the ground surface during an earthquake.
- Love waves are fast and move the ground from side to side.
Body waves travel through the Earth.
- P-waves are the fastest type of seismic wave. As P-waves travel, the surrounding rock is repeatedly compressed and then stretched.
- S-waves arrive after P-waves because they travel more slowly. The rock is shifted up and down or side to side as the wave travels through it.
Shop Windows to the Universe Science Store!
The
Fall 2010 issue of The Earth Scientist, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!
You might also be interested in:
The expression "on solid ground" is often used to describe something as stable. Usually the solid ground underfoot seems very stable. But sometimes it is not. "The ground seemed to twist under us like
...more
At 5:12 am on Wednesday April 18, 1906 most people in San Francisco, CA were still asleep. But they were about to wake up very suddenly. The Earth shook violently - an earthquake. It lasted for only about
...more
Spotting minerals is fun! There are many different types of minerals, each with a different name and a special set of characteristics. So, if you find a mineral that you do not recognize, you can use
...more
Quartz is one of the most common mineral in Earth’s crust! Silica (Si) and Oxygen (O) are the only elements within pure quartz. If a cooling magma has silica leftover after feldspars form, quartz is likely
...more
Mica minerals make some rocks sparkle! They are often found in igneous rocks such as granite and metamorphic rocks such as schist. They sparkle because light is reflected on their flat surfaces, which
...more
Feldspar is the most common mineral in the Earth’s crust, so you are very likely to find it in the rocks you collect! It is found it all of the three rock types, but is most common in intrusive igneous
...more
Olivine looks like little green crystals. It is typically found in some igneous and metamorphic rocks. Often the crystals are so small that you need to use your hand lens or magnifying glass to see them
...more
