Use this guide to investigate why earthquakes happen, how they've Look at the Seismic Waves video and discuss with a friend how P and Earthquake diagram , describe the relationship between the faults and the plates. On Monday evening (May 14), there was a magnitude earthquake along the fault centered just east of Oakland. It comes just over four. To watch a video flyover of the Greendale Fault in Canterbury click here. The relationship between earthquakes and faults was first established by nineteenth.
The sudden upward or downward movement of the seafloor during an earthquake creates large tsunami waves, similar to a child splashing in the bathtub. Earthquakes can also trigger tsunamis by unleashing underwater landslides, which also displace huge amounts of seawater. In this photo taken by a tourist Eric Skitzi from England, tourists watch as tsunami waves hit the shore from a safe place inside Casuarina Beach Hotel resort in Penang, northwestern Malaysia around 1: The resort hotel lifeguards noticed waves were huge and sounded warning to all tourists around the hotel beach area to run to the safety area.
The Malaysian government on Wednesday canceled New Year celebrations nationwide, urging people to pray this weekend that the country will be spared from future disasters such as the recent tsunamis that killed at least 65 Malaysians.
Earthquakes & Tsunamis: Causes & Information
Because these faults extend from the surface down to several miles deep, geologists can't simply visit the source to calculate these numbers. Instead, they rely on a tool known as a seismograph, which measures seismic waves, or vibrations, from an earthquake.
An earthquake's magnitude is ranked on the moment magnitude scale, not the Richter scale. The moment magnitude scale provides a better idea of the shaking and possible damage from earthquakes of all kinds around the world.
Whatever Happened to the Richter Scale?
Earthquakes & Tsunamis: Causes & Information
A magnitude of 3 to 5 is considered minor, while a quake with a magnitude of 5 to 7 is moderate to strong. At the higher end, these quakes can be destructive to cities. Earthquakes from 7 to 8 are major; about 15 of these occur annually. Every year, at least one earthquake with a magnitude over 8 — a "great" quake — wreaks havoc. An earthquake with a magnitude of 10 has never been measured, but it would create widespread devastation.
Devastating Earthquake Visualized ] By using the readings from at least three seismographs, geologists can triangulate the origin of the earthquake. At the fault, that origin is called the hypocenter; on the surface, the epicenter. Most of the major earthquakes strike on well-known fault lines.
Californians, for instance, are unlikely to be shocked if they feel the ground shuddering beneath their feet.
But a draft map released by the U. More than years of earthquakes glow on a world map. Preparing for disaster Scientists have not yet come up with a way to forecast earthquakes. Although animals are reputed to have a sixth sense when it comes to these vibrations, no research has confirmed it, much less determined how such predictions might occur.
In many cases, animals are simply sensing the arrival of earthquake waves that go unnoticed by people. However, scientists can identify locations that are likely to experience earthquakes in the future. For instance, along the tectonic plate boundary off the western shore of South America, researchers have mapped the location of historical earthquakes and found " seismic gaps " — zones with no recent large earthquake quakes.
And indeed, scientists had forecast a major earthquake in a seismic gap near Maule, Chile, which was hit by a magnitude Even without such forecasts, there are some basic things that can be done to prepare for an earthquake.
- Earthquakes and Faults
The Federal Emergency Management Agency recommends that all families everywhere should have an emergency kit in their home and car, and communicate with your loved ones a plan for any type of disaster not just for earthquakes. Such preparation can make a difference not only physically, but also emotionally. Keep heavy objects away from beds and sitting areas, and fasten fixtures such as large televisions to the walls.
Locate a safe place in each room, under a sturdy desk or table, where you can seek refuge from falling objects.
If you are outside, get into an open area, away from structures or bridges. According to FEMA, many deaths in the Long Beach earthquake occurred when people ran outside, only to be crushed by falling debris from collapsing structures. In any earthquake cluster, the largest one is called the mainshock; anything before it is a foreshock, and anything after it is an aftershock. Aftershocks are earthquakes that usually occur near the mainshock.Earthquakes Tectonic Plates and Fault Lines
The stress on the mainshock's fault changes during the mainshock and most of the aftershocks occur on the same fault. Sometimes the change in stress is great enough to trigger aftershocks on nearby faults as well.
An earthquake large enough to cause damage will probably produce several felt aftershocks within the first hour. The rate of aftershocks dies off quickly. The day after the mainshock has about half the aftershocks of the first day. Ten days after the mainshock there are only a tenth the number of aftershocks. An earthquake will be called an aftershock as long as the rate of earthquakes is higher than it was before the mainshock.
For big earthquakes this might go on for decades. Bigger earthquakes have more and larger aftershocks.
The bigger the mainshock, the bigger the largest aftershock, on average, though there are many more small aftershocks than large ones. Also, just as smaller earthquakes can continue to occur a year or more after a mainshock, there is still a chance for a large aftershock long after an earthquake.
Foreshocks Sometimes what we think is a mainshock is followed by a larger earthquake.
Earthquakes and Faults / Earthquakes / Science Topics / Learning / Home - GNS Science
Then the original earthquake is considered a foreshock. The chance of this happening dies off quickly with time just like aftershocks.
After three days the risk is almost gone. Sometimes, the chance that an event is a foreshock seems higher than average - usually because of its proximity to a major fault. The California Emergency Management Agency will then issue an advisory based on scientists' recommendations. These are the only officially recognized short-term "predictions. Earthquakes occur on faults. A fault is a thin zone of crushed rock separating blocks of the earth's crust. When an earthquake occurs on one of these faults, the rock on one side of the fault slips with respect to the other.
Faults can be centimeters to thousands of kilometers long. The fault surface can be vertical, horizontal, or at some angle to the surface of the earth. Faults can extend deep into the earth and may or may not extend up to the earth's surface.
How do we know a fault exists? Past fault movement has brought together rocks that used to be farther apart; Earthquakes on the fault have left surface evidence, such as surface ruptures or fault scarps cliffs made by earthquakes ; Earthquakes recorded by seismographic networks are mapped and indicate the location of a fault. Some faults have not shown these signs and we will not know they are there until they produce a large earthquake.
Several damaging earthquakes in California have occurred on faults that were previously unknown. Surface features that have been broken and offset by the movement of faults are used to determine how fast the faults move and thus how often earthquakes are likely to occur.
For example, a streambed that crosses the San Andreas fault near Los Angeles is now offset 83 meters 91 yards from its original course.