Table of Contents

## How is the time of an earthquake determined?

If you want to determine the “Origin Time” (actual time the earthquake occurred at the source), take the s-p times above and multiply by 1.37. Take this time and subtract that from the P arrival time to get the approximate origin time.

**How are S waves and P waves used to determine how far away epicenters are?**

Each seismograph records the times when the first (P waves) and second (S waves) seismic waves arrive. From that information, scientists can determine how fast the waves are traveling. Knowing this helps them calculate the distance from the epicenter to each seismograph.

**How do you find the lag time of P and S waves?**

To find lag time for earthquake waves at 100 km, subtract the time it takes P waves to travel 100 km from the time it takes S waves to travel 100 km. Record the lag time.

### What is the SP time?

In earthquake seismology, the time interval between the first arrivals of transverse (S) and longitudinal (P) waves, which is proportional to the distance from the earthquake source.

**What is the longest earthquake time?**

1960 Valdivia earthquake

Iquique Santiago Punta Arenas | |
---|---|

UTC time | 1960-05-22 19:11:14 |

Local date | 22 May 1960 |

Local time | 15:11:14 |

Duration | approx. 10 minutes |

**What is the time difference between P and S waves?**

S waves are indicated by an abrupt change in wave amplitude. In the seismogram below, we see that the S wave arrived at about 34 sec after the P wave arrived. This time difference is called the S-P interval and is the lag time between the P and S wave.

#### How does the P & S wave amplitude and magnitude vary with distance from the earthquake epicenter?

Therefore, the farther a seismic recording station is from the earthquake epicenter the greater will be the difference in time of arrival between the P and S wave. The Richter magnitude is recorded on a logarithmic scale on which an increase of one represents a ten times increase in amplitude.

**How do you calculate time lag?**

Time = Distance / Speed So, the lag time difference between the two vehicles (10 hours – 5 hours) is 5 hours. What would the lag time be if the distance traveled were 500 miles? Vehicle A would take 10 hours to travel 500 miles, but Vehicle B would take 20 hours. The lag time here is 10 hours.

**What is the lag time or the SP interval?**

## How do you get time difference in the arrival time of P wave and S wave?

As the P and S waves travel out from an earthquake the P waves get progressively farther ahead of the S waves. Therefore, the farther a seismic recording station is from the earthquake epicenter the greater will be the difference in time of arrival between the P and S wave.

**How do you solve time difference in the arrival time of P wave and S wave?**

7) If you are asked to determine the arrival time of the P-wave and given a clock time for the arrival of the S-wave: Find difference in arrival time between P-wave and S-wave at the given epicenter distance, Subtract the difference in arrival time from the clock time of the S-wave.

**How long does it take an earthquake to reach the epicenter?**

The difference in arrival times for the P and S- waves from an earthquake is 5.0 minutes. According to the Earth Science Reference Tables, how far away is the epicenter of the earthquake? A seismographic station determines that the distance from the epicenter of an earthquake is 4,000 kilometers.

### When is the first S wave of an earthquake recorded?

A seismic station records the first S-wave at 12:19 p.m. Which set of data shows the approximate arrival time of the first P -wave and the distance to the epicenter? A seismic P -wave is recorded at 2:25 p.m. at a seismic station located 7600 kilometers from the epicenter of an earthquake.

**Where does an earthquake occur in the world?**

Earthquakes can strike any location at any time. But history shows they occur in the same general patterns year after year, principally in three large zones of the earth.

**How is the probability of an earthquake determined?**

USGS scientists can only calculate the probability that a significant earthquake will occur in a specific area within a certain number of years. An earthquake prediction must define 3 elements: 1) the date and time, 2) the location, and 3) the magnitude.