## What does peak ground acceleration mean?

Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location.

PGA is equal to the amplitude of the largest absolute acceleration recorded on an accelerogram at a site during a particular earthquake.

## What is spectral response acceleration?

Spectral acceleration (SA) is a unit measured in g (the acceleration due to Earth’s gravity, equivalent to g-force) that describes the maximum acceleration in an earthquake on an object – specifically a damped, harmonic oscillator moving in one physical dimension.

## What does Richter earthquake magnitude measure?

Richter scale (ML), quantitative measure of an earthquake’s magnitude (size), devised in 1935 by American seismologists Charles F. Richter and Beno Gutenberg. The earthquake’s magnitude is determined using the logarithm of the amplitude (height) of the largest seismic wave calibrated to a scale by a seismograph.

## What are some earthquake hazards?

earthquake hazard. Earthquake hazard is anything associated with an earthquake that may affect the normal activities of people. This includes surface faulting, ground shaking, landslide, liquefaction, tectonic deformation, tsunamis, and seiches.

## What is instrumental intensity?

The frequency-dependent spectrum based seismic intensity, also called instrumental intensity, is calculated basically from the integration of the square values of spectral acceleration ordinates.

## What is recurrence interval?

From Wikipedia, the free encyclopedia. A return period, also known as a recurrence interval or repeat interval, is an average time or an estimated average time between events such as earthquakes, floods, landslides, or a river discharge flows to occur.

## How bad is a 7.0 earthquake?

Strong: 6 – 6.9. A strong earthquake is one that registers between 6 and 6.0 on the Richter scale. There are about 100 of these around the world every year and they usually cause some damage. In populated areas, the damage may be severe.

## How far away can you feel a 7.0 earthquake?

A magnitude-5.5 quake in the Eastern United States can usually be felt as far away as 300 miles (500 km), the service’s website says. The nature of the crust under eastern North America determines how far an earthquake is felt, Presgrave said.

## Is a 10.0 earthquake possible?

No known faults are long enough to generate a megaquake of 10 or more. (The largest quake ever recorded was a magnitude 9.5.) According to the U.S. Geological Survey, computer models indicate the San Andreas Fault is capable of producing earthquakes up to about 8.3.

## What are the 5 earthquake hazards?

These include ground shaking, landslides, liquefaction, and in some areas, tsunamis. These primary hazards often produce secondary hazards such as ruptured utility lines, hazardous spills, and fires. Buildings can crumble or collapse, trapping people inside and burying streets in rubble.

## What are the four earthquake hazards?

Primary earthquake hazards are: ground shaking. landslides. liquefaction.

Secondary earthquake hazards are those that are caused by the primary hazards, and may often be more catastrophic:

- tsunami.
- seiche.
- flooding.
- fire.

## What are three effects of earthquakes?

Effects of Earthquakes. The primary effects of earthquakes are ground shaking, ground rupture, landslides, tsunamis, and liquefaction. Fires are probably the single most important secondary effect of earthquakes.

## What is the minimum number of seismic stations needed to find the location of an earthquake?

To locate the epicenter of an earthquake, scientists must have seismograms from at least three seismic stations. The procedure for locating an epicenter has three steps: Scientists find the difference between the arrival times of the primary and the secondary waves at each of the three stations.

## How do you calculate recurrence rate?

Count the total number of years on record. Use the formula: Recurrence Interval equals the number of years, plus one, divided by the magnitude rank for which you wish to calculate the recurrence interval. Plug in your data to calculate the recurrence interval.

## How is a 100 year flood determined?

The term “100-year flood” is used in an attempt to simplify the definition of a flood that statistically has a 1-percent chance of occurring in any given year. Likewise, the term “100-year storm” is used to define a rainfall event that statistically has this same 1-percent chance of occurring.

## How often does a 100 year flood occur?

Do they really occur only once in 100 years? The name is misleading: a “100-year flood” does not happen only once every 100 years. The name describes the estimated probability of that particular flood happening in any given year. A 100-year event has a 1 percent chance of occurring in any given year.

## How long does a 7.0 earthquake last?

Generally, only seconds. Strong ground shaking during a moderate to large earthquake typically lasts about 10 to 30 seconds. Readjustments in the earth cause more earthquakes (aftershocks) that can occur intermittently for weeks or months.

## How far away can a 9.0 earthquake be felt?

Interestingly enough though, deep focus earthquakes can occur at depths of hundreds of miles and can be felt literally half a world away. The 2013 Okhotsk Sea Earthquake had it’s epicenter off the coast Russia north of Japan at a depth of 609 km (380 miles), with strong shaking felt as far away as Moscow.

## What’s the highest earthquake level?

The biggest earthquake ever recorded was a magnitude 9.5. It occurred in 1960 in Chile, where the Nazca plate subducts under the South American plate. There is no theoretical limit to the magnitude of an earthquake, although it is estimated that an earthquake of magnitude 11 would split the Earth in two.