Seismology Flashcards

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Questions and Answers

What is the study of earthquakes and seismic waves called?

Seismology

What does a seismograph record?

Vibrations in the ground

Name the types of motion that a modern three-component seismograph records.

Vertical and horizontal motion

How do seismographs record motion?

By tracking wave-shaped lines on paper or translating the motion into electromagnetic signals Signup and view all the answers

A tracing of earthquake motion that is recorded by a seismograph is called a(n)?

Seismogram Signup and view all the answers

Why are P waves the first waves to be recorded by a seismograph?

Because they are the fastest-moving seismic waves Signup and view all the answers

Which type of wave is the second wave to be recorded by a seismograph?

S waves Signup and view all the answers

What types of waves are the slowest, and therefore the last to be recorded by a seismograph?

Surface waves, or Rayleigh and Love waves Signup and view all the answers

Scientists determine the distance to an epicenter by analyzing?

The arrival times of the P waves and the S waves Signup and view all the answers

The longer the lag time between the arrival of the P waves and the S waves indicates?

The farther away the earthquake occurred Signup and view all the answers

Scientists consult a lag-time graph to determine how far an earthquake occurred from?

A given seismograph station Signup and view all the answers

A lag-time graph translates the difference in arrival times of the P waves and S waves into distance from the epicenter to?

Each station Signup and view all the answers

What does a lag-time graph determine about an earthquake?

Its start time Signup and view all the answers

Before computers were widely available, how did scientists locate the epicenter of an earthquake?

By drawing circles around at least three seismograph stations on a map Signup and view all the answers

On the early maps, the radius of each circle was equal to what?

The distance from that station to the earthquake's epicenter Signup and view all the answers

Where would the epicenter of the earthquake be found on the map?

At the point where all circles intersected Signup and view all the answers

Scientists who study earthquakes are interested in the amount of?

Energy released by an earthquake Signup and view all the answers

Magnitude refers to?

The measure of the strength of an earthquake Signup and view all the answers

What is the Richter scale?

A measurement system that bases earthquake strength on ground motion Signup and view all the answers

What does the moment magnitude measure?

The strength of the earthquake based on the size of the fault area that moves Signup and view all the answers

Intensity measures?

The amount of danger caused by an earthquake Signup and view all the answers

What is the Mercalli scale?

A measurement system that expresses earthquake intensity in Roman numerals Signup and view all the answers

Which magnitude scale was widely used for most of the 20th century?

Richter scale Signup and view all the answers

Which magnitude scale do scientists generally prefer now?

Moment magnitude scale Signup and view all the answers

The Richter scale and the moment magnitude scale provide similar values for?

Small earthquakes Signup and view all the answers

The moment magnitude scale is more accurate for measuring?

Large earthquakes Signup and view all the answers

What was the highest moment magnitude recorded for an earthquake so far?

9.5 Signup and view all the answers

What was the moment magnitude of the quake in Kobe, Japan, in 1995?

6.9 Signup and view all the answers

What is the moment magnitude of earthquakes that generally are not felt by people?

Less than 2.5 Signup and view all the answers

How is intensity I described on the modified Mercalli intensity scale?

Expresses intensity in Roman numerals from I to XII Signup and view all the answers

How is intensity XII described on the modified Mercalli intensity scale?

As total destruction Signup and view all the answers

Study Notes

Seismology Overview

Seismology is the scientific study of earthquakes and seismic waves.
Seismographs are instruments used to record ground vibrations.

Seismograph Functionality

Modern three-component seismographs record vertical and horizontal ground motion:
- One device for vertical motion.
- Two devices for horizontal motion (east-west and north-south).
Seismographs track motion either on paper via wave-shaped lines or through electromagnetic signals.

Seismograms and Wave Types

A seismogram is the recorded tracing of earthquake motion.
P waves (Primary waves) are the fastest seismic waves and the first to be recorded.
S waves (Secondary waves) follow P waves as the second type recorded.
Surface waves, which include Rayleigh and Love waves, are the slowest and last to be recorded.

Determining Epicenter Distance

The distance to an earthquake's epicenter is determined by analyzing the arrival times of P and S waves.
A longer lag time between P and S waves indicates a greater distance from the seismograph to the epicenter.
Lag-time graphs illustrate the difference in arrival times to calculate distances from the epicenter to each station.

Locating Earthquake Epicenters

Historically, finding an epicenter involved drawing circles around at least three seismograph stations on a map.
The intersection of circles from these stations pinpointed the epicenter's location.

Earthquake Energy and Magnitude

The energy released by an earthquake is of primary interest to seismologists.
Magnitude measures the strength of an earthquake.
The Richter scale measures earthquake strength based on ground motion, widely used in the 20th century.
The moment magnitude scale measures earthquake strength more accurately, focusing on fault area size, average fault displacement, and rock rigidity.

Intensity and Measurement Scales

Intensity refers to the level of danger caused by an earthquake.
The Mercalli scale assesses earthquake intensity in Roman numerals, detailing the effects associated with each level.

Preference for Magnitude Scales

The Richter scale and moment magnitude scale yield similar values for small earthquakes.
The moment magnitude scale is preferred, especially for evaluating large earthquakes, providing accuracy.

Record-Breaking Magnitudes

The highest recorded moment magnitude for an earthquake is 9.5.
The 1995 Kobe, Japan earthquake had a moment magnitude of 6.9.
Earthquakes with a moment magnitude of less than 2.5 are generally not felt by people.

Intensity Descriptions

The modified Mercalli intensity scale classifies intensity from I to XII, describing effects at each level.
Intensity I indicates minimal effects, while intensity XII signifies total destruction.

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Description

Explore the fascinating field of seismology with these flashcards. Test your knowledge on key terms such as seismographs and various types of ground motion. Perfect for students looking to deepen their understanding of earthquakes and seismic activity.