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What to REALLY expect during an earthquake

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What to REALLY expect during an earthquake

Each year, the residents of Earthquake Country feel many minor earthquakes. Below are descriptions on what you may experience in one of these earthquakes. On rare occasions larger earthquakes do happen.

Statistics on the annual number of earthquakes for each magnitude

Things you might see during an earthquake

* Hanging plants or lights moving or swaying
* Things falling off shelves or pictures falling off the wall
* Cabinets opening and shutting
* Trees swaying back and forth

Things you might hear during an earthquake

* Things rattling or banging
* Things falling off of shelves
* The building creaking
* Car alarms going off

Things you might feel during an earthquake

* Scared or confused
* You may feel a shaking, jolting or rolling motion
* It may be hard to walk


Modified Mercalli Scale of Intensity

The Modified Mercalli Scale of Intensity is a measure of what is felt during the earthquake and the resulting damage. The intensity of an earthquake loosely correlates with the size of an earthquake. Some factors which cause the intensity to vary from magnitude include: distance from the earthquake, soil type, local population, building density and structure quality.

Modified Mercali Scale
I. People do not feel any Earth movement.
II. A few people indoors feel movement if they are at rest and/or on the upper floors of tall buildings.
III. Many people indoors feel movement. Hanging objects swing back and forth. People outdoors might not realize that an earthquake is occurring.
IV. Most people indoors feel movement. Hanging objects swing. Dishes, windows, and doors rattle. The earthquake feels like a heavy truck hitting the walls. A few people outdoors may feel movement. Parked cars rocked.
V. Almost everyone feels movement. Sleeping people are awakened. Doors swing open or close. Dishes are broken. Pictures on the wall move. Small objects move or are turned over. Trees might shake. Liquids might spill out of open containers.
VI. Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster in walls might crack. Tress and bushes shake. Damage is slight in poorly built buildings. No structural damage.
VII. People have difficulty standing. Drivers feel their cars shake. Some furniture breaks. Loose bricks fall from buildings. Damage is slight to moderate in well-built buildings, considerable in poorly-built buildings.
VIII. Drivers have trouble steering. Houses that are not bolted down might shift on their foundations. Tall structures such as towers and chimneys might twist and fall. Well-built buildings suffer moderate damage. Poorly-built structures suffer severe damage. Tree branches break. Hillsides might crack if the ground is wet. Water level in wells might change.
IX. Well-built buildings suffer considerable damage. Houses that are not bolted down move off their foundations. Some underground pipes are broken. The ground cracks. Reservoirs suffer serious damage.
X. Most buildings and their foundations are destroyed. Some bridges are destroyed. Dams are seriously damaged. Large landslides occur. Water is thrown on the banks of canals, rivers, and lakes. The ground cracks in large areas. Railroad tracks are bent slightly.
XI. Most buildings collapse. Some bridges are destroyed. Large cracks appear in the ground. Underground pipelines are destroyed. Railroad tracks are badly bent.
XII Almost everything is destroyed. Objects are thrown in the air. The ground moves in waves or ripples. Large amounts of rock may move.

This is an intensity map for the M6.7 Northridge earthquake in southern California.

This is an intensity map for a M2.8 earthquake in southern California.
Notice the difference in areas that felt shaking, and how much less the intensity was.

Why are the maps blocky?

The map is created by people answering questions on a survey. An intensity for their location is determined based upon their answers. The survey asks for people's zip codes. The intensity for each zip code is an average of all responses received. The boarders/boxes you see on the map are the zip code boundaries.

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