Earthquake Engineering Exam 1

Front 1

A type of seismograph used to measure ground acceleration as a function of time.

Back 1

Accelerograph

Front 2

A fault along which slip has occurred in recent geological time, or where earthquake foci are located.

Back 2

Active fault

Front 3

Continental margin characterized by earthquakes and volcanic activity (i.e. location of transform fault or subduction zone).

Back 3

Active margin

Front 4

An earthquake that occurs after a "mainshock" (or larger earthquake).

Back 4

Aftershock

Front 5

The maximum height of a wave crest or depth of a trough.

Back 5

Amplitude (wave)

Front 6

An ordered arrangement of seismometers or geophones, the data from which feeds into a central receiver.

Back 6

Array

Front 7

The appearance of seismic energy on a seismic record.

Back 7

Arrival

Front 8

The time at which a particular wave phase arrives at a detector.

Back 8

Arrival time

Front 9

Not associated with an earthquake

Back 9

Aseismic

Front 10

Area with no record of earthquakes

Back 10

Aseismic zone

Front 11

Roughness on the fault surface posing local resistance to slip.

Back 11

Asperities (fault)

Front 12

The layer below the lithosphere that is marked by low seismic-wave velocities and high seismic- wave attenuation.

Back 12

Asthenosphere

Front 13

The reduction in amplitude of a wave with time or distance travelled.

Back 13

Attenuation

Front 14

A plane orthogonal to the fault plane.

Back 14

Auxiliary fault-plane

Front 15

An area of fault surface that is resistant to slip because of geometrical or structural changes.

Back 15

Barrier (fault)

Front 16

A narrow zone, defined by earthquake foci, that is tens of kilometers thick dipping from the surface under the Earth's crust to depths of up to 700 kilometers.

Back 16

Benioff zone / Wadati-Benioff zone

Front 17

A deep crustal thrust-fault with no or only indirect surface expression such as a fold structure.

Back 17

Blind thrust

Front 18

A seismic wave that can travel through the interior of the earth.

Back 18

Body wave

Front 19

Examples of body waves

Back 19

P-waves and S-waves

Front 20

Magnitude of an earthquake as estimated from the amplitude of body waves.

Back 20

Body-wave magnitude

Front 21

A fault along which it is mechanically feasible for sudden slip to occur.

Back 21

Capable fault

Front 22

The mass per unit volume of a substance, commonly expressed in grams per cubic centimetre.

Back 22

Density

Front 23

The value given is the depth below the surface of the mean spheroid.

Back 23

Depth of an earthquake

Front 24

The increase in the volume of rocks mainly due to pervasive microcracking.

Back 24

Dilatancy (of rocks)

Front 25

The angle by which a rock layer or fault plane deviates from the horizontal. The angle is measured in a plane perpendicular to the strike.

Back 25

Dip

Front 26

A fault in which the relative displacement is along the direction of dip of the fault plane; the offset is either normal or reverse.

Back 26

Dip-slip fault

Front 27

The spreading out of a wave train due to each wavelength travelling with its own velocity.

Back 27

Dispersion (wave)

Front 28

Time interval between the first and last peaks of strong ground motion above a specified amplitude.

Back 28

Duration (of strong shaking)

Front 29

The sudden release of stored elastic energy caused by the sudden fracture and movement of rocks along a fault. Some of the energy released is in the form of seismic waves, that cause the ground to shake.

Back 29

Earthquake

Front 30

The average interval of time between the occurrence of earthquakes in a particular region.

Back 30

Earthquake occurrence (recurrence) interval

Front 31

A series of minor earthquakes, none of which may be identified as the main shock, occurring in a limited area and time.

Back 31

Earthquake swarm

Front 32

An earthquake with a size and generating mechanism typical for a particular fault source.

Back 32

Characteristic earthquake

Front 33

The layer of rock located immediately below the earth's surface. Beneath continents, it is typically about 35 km thick, and composed of granite. Under the ocean, it is about 5-10 kilometres thick and composed mainly of basalt.

Back 33

Earth's crust

Front 34

A wave that is propagated by some kind of elastic deformation, that is, a change in shape that disappears when the stresses are removed. A seismic wave is a type of this.

Back 34

Elastic wave

Front 35

The concluding train of seismic waves that follows the principal waves from an earthquake.

Back 35

Coda

Front 36

Tightly packed. Composed of particles that are not easily separated.

Back 36

Consolidated

Front 37

The theory, first advanced by Alfred Wegener, that Earth's continents were originally one land mass. Pieces of the land mass split off and migrated to form the continents.

Back 37

Continental Drift

Front 38

Part of the continental margin between the coast and the continental slope.

Back 38

Continental shelf

Front 39

The innermost layers of the Earth.

Back 39

Core

Front 40

Solid and has a radius of about 1300 kilometres

Back 40

Inner core

Front 41

Fluid and is about 2300 kilometres thick. S-waves cannot travel through

Back 41

Outer core

Front 42

Loss of energy in wave motion due to transfer into heat by frictional forces.

Back 42

Damping

Front 43

The mass per unit volume of a substance, commonly expressed in grams per cubic centimetre.

Back 43

Density

Front 44

The layer of rock located immediately below the earth's surface. Beneath continents, it is typically about 35 km thick, and composed of granite. Under the ocean, it is about 5-10 kilometres thick and composed mainly of basalt.

Back 44

Earth's crust

Front 45

A wave that is propagated by some kind of elastic deformation, that is, a change in shape that disappears when the stresses are removed. A seismic wave is a type of this.

Back 45

Elastic wave

Front 46

The point on the earth's surface directly above the focus (hypocentre) of an earthquake.

Back 46

Epicentre

Front 47

A zone of fractures or breaks in rocks, where movements occur. Earthquakes often occur along these because they are weak zones in the rock.

Back 47

Fault

Front 48

The plane that most closely coincides with the rupture surface of a fault.

Back 48

Fault plane

Front 49

The first recorded signal attributed to seismic wave travel from a source.

Back 49

First arrival

Front 50

More-or-less symmetrical splays into sub-faults near the intersection of the main fault with the ground surface.

Back 50

Flower structure

Front 51

An earthquake that is smaller than, and precedes, a "mainshock".

Back 51

Foreshock

Front 52

Number of oscillations per unit time; unit is Hertz (Hz),which equals 1 cycle per second.

Back 52

Frequency

Front 53

In a fault zone, crushed, sheared, and powdered rock altered to clay.

Back 53

Gouge

Front 54

The value given is the depth below the surface of the mean spheroid.

Back 54

Depth of an earthquake

Front 55

A crustal block of rock generally long and narrow, that has dropped down along boundary faults relative to the adjacent rocks.

Back 55

Graben

Front 56

An earthquake having a magnitude of 8 or greater on the Richter scale.

Back 56

Great Earthquake

Front 57

Discontinuity in seismic velocity that marks the boundary between the core and the mantle.

Back 57

Gutenberg discontinuity

Front 58

A situation that has the possibility of occurring.

Back 58

Hazard

Front 59

The unit of frequency equal to 1 cycle per second, or 2 PI radians per second.

Back 59

Hertz

Front 60

The current geological time period that started about 10,000 years ago.

Back 60

Holocene

Front 61

The subsurface location (focus) at which the energy of an earthquake is released. Earthquakes generally occur at depths less than about 30 km, but may occur to a depth of 600 km or more in some areas.

Back 61

Hypocentre

Front 62

An index of the resistance of an elastic body, such as a rock, to volume change.

Back 62

Incompressibility

Front 63

Central solid region of the Earth's core, probably mostly iron; radius about 1221 kilometers, discovered by Inge Lehmann in 1936.

Back 63

Inner core

Front 64

The Modified Mercalli Scale is a numerical scale used to catagorize earthquakes based on descriptions of how the earthquake was felt. These effects may range from I (not felt except by a very few under especially favourable conditions) and XII (total damage).

Back 64

Intensity

Front 65

The increase in the volume of rocks mainly due to pervasive microcracking.

Back 65

Dilatancy (of rocks)

Front 66

Earthquake with its focus on a plate boundary. Offshore earthquakes of western Canada are of this type.

Back 66

Interplate earthquake

Front 67

The angle by which a rock layer or fault plane deviates from the horizontal. The angle is measured in a plane perpendicular to the strike.

Back 67

Dip

Front 68

A fault in which the relative displacement is along the direction of dip of the fault plane; the offset is either normal or reverse.

Back 68

Dip-slip fault

Front 69

The spreading out of a wave train due to each wavelength travelling with its own velocity.

Back 69

Dispersion (wave)

Front 70

Time interval between the first and last peaks of strong ground motion above a specified amplitude.

Back 70

Duration (of strong shaking)

Front 71

The sudden release of stored elastic energy caused by the sudden fracture and movement of rocks along a fault. Some of the energy released is in the form of seismic waves, that cause the ground to shake.

Back 71

Earthquake

Front 72

The average interval of time between the occurrence of earthquakes in a particular region.

Back 72

Earthquake occurrence (recurrence) interval

Front 73

A series of minor earthquakes, none of which may be identified as the main shock, occurring in a limited area and time.

Back 73

Earthquake swarm

Front 74

Earthquake with its focus within a tectonic plate. Eastern Canadian earthquakes are of this type.

Back 74

Intraplate earthquake

Front 75

A surface wave which travels through the continental crust. This wave type is the one which causes damage during large Eastern Canadian earthquakes.

Back 75

Lg Wave

Front 76

Chain of islands above a subduction zone (e.g., Japan, Aleutians).

Back 76

Island arc

Front 77

A line connecting points on the Earth's surface at which earthquake intensity is the same. It is usually a closed curve around the epicentre.

Back 77

Isoseismal Line

Front 78

The way in which the lithosphere 'floats' on the asthenosphere.

Back 78

Isostasy

Front 79

An abrupt movement of geological materials downhill in response to gravity. It can be triggered by an earthquake or other natural causes.

Back 79

Landslide

Front 80

The location of a point north or south of the equator.It is shown on a map or globe as east-west lines parallel to the equator.

Back 80

Latitude

Front 81

A strike-slip fault on which the displacement of the far block is to the left when viewed from either side.

Back 81

Left-lateral fault: (sinistral)

Front 82

The process in which a granular solid (soil) takes on the characteristics of a liquid as a result of an increase in pore pressure and a reduction in stress. In other words, solid ground loses cohesion and starts flowing like a liquid.

Back 82

Liquefaction

Front 83

Physical character of rocks.

Back 83

Lithology

Front 84

The outer, rigid shell of the Earth above the asthenosphere. It contains the crust, continents, and plates.

Back 84

Lithosphere

Front 85

Earthquake with its focus within a tectonic plate. Eastern Canadian earthquakes are of this type.

Back 85

Intraplate earthquake

Front 86

A surface wave which travels through the continental crust. This wave type is the one which causes damage during large Eastern Canadian earthquakes.

Back 86

Lg Wave

Front 87

The location of a point east or west of the prime meridian. It is shown on a map or globe as north-south lines left and right of the prime meridian, which passes through Greenwich, England.

Back 87

Longitude

Front 88

A major type of surface wave having a horizontal motion that is shear or transverse to the direction of propagation (travel).

Back 88

Love wave

Front 89

Any layer in the Earth in which seismic wave velocities are lower than in the layers above and below.

Back 89

Low-velocity zone

Front 90

It is a measure of the amount of energy released during an earthquake. It may be expressed using the Richter scale.

Back 90

Magnitude

Front 91

The largest earthquake in a "cluster" of earthquakes. These are sometimes preceded by "foreshocks", and generally followed by aftershocks.

Back 91

Mainshock

Front 92

An earthquake having a magnitude of 7 to 7.99 on the Richter scale.

Back 92

Major Earthquake

Front 93

The main bulk of the Earth, between the crust and the core, ranging from depths of about 40 to 3470 kilometres. It is composed of dense silicate rocks and divided into a number of concentric shells. Under Eastern Canada, it can be found at around 40 km depth.

Back 93

Mantle (of Earth)

Front 94

The area of strong shaking and significant damage in an earthquake.

Back 94

Meizoseismal region

Front 95

An earthquake having a magnitude of 2 or less on the Richter scale.

Back 95

Microearthquake

Front 96

Chain of islands above a subduction zone (e.g., Japan, Aleutians).

Back 96

Island arc

Front 97

A more or less continuous motion in the Earth that is unrelated to an earthquake and that has a period of 1.0 to 9.0 seconds. It is caused by a variety of natural and artificial agents.

Back 97

Microseism

Front 98

The division of a town or county into smaller areas according to their variation in seismic hazard.

Back 98

Microzonation

Front 99

An earthquake having a magnitude of 5 to 6 on the Richter scale.

Back 99

Moderate earthquake

Front 100

The Mercalli scale rates the intensity of shaking from an earthquake. The ratings vary from I (felt only under especially favourable circumstances) to XII (total destruction).

Back 100

Modified Mercalli Intensity Scale

Front 101

The boundary surface or sharp seismic-velocity discontinuity that separates the Earth's crust from the underlying mantle. Under Eastern Canada, it can be found at around 40 km depth.

Back 101

Mohorovicic discontinuity (the Moho):

Front 102

A measure of earthquake size related to the leverage of the forces (couples) across the area of the fault slip. The rigidity of the rock times the area of faulting times the amount of slip. Dimensions are dyne-cm (or Newton-metres).

Back 102

Moment (of earthquakes):

Front 103

Magnitude of an earthquake estimated by using the seismic moment.

Back 103

Moment magnitude (MW)

Front 104

A dip-slip fault in which the rock above the fault plane has moved downward with respect to the rock below.

Back 104

Normal fault

Front 105

The slip on the fault has components both along the dip and along the strike of the fault.

Back 105

Oblique faulting

Front 106

The exact time at which an earthquake occurred.

Back 106

Origin time

Front 107

A line connecting points on the Earth's surface at which earthquake intensity is the same. It is usually a closed curve around the epicentre.

Back 107

Isoseismal Line

Front 108

The way in which the lithosphere 'floats' on the asthenosphere.

Back 108

Isostasy

Front 109

An abrupt movement of geological materials downhill in response to gravity. It can be triggered by an earthquake or other natural causes.

Back 109

Landslide

Front 110

The location of a point north or south of the equator.It is shown on a map or globe as east-west lines parallel to the equator.

Back 110

Latitude

Front 111

A strike-slip fault on which the displacement of the far block is to the left when viewed from either side.

Back 111

Left-lateral fault: (sinistral)

Front 112

The process in which a granular solid (soil) takes on the characteristics of a liquid as a result of an increase in pore pressure and a reduction in stress. In other words, solid ground loses cohesion and starts flowing like a liquid.

Back 112

Liquefaction

Front 113

Physical character of rocks.

Back 113

Lithology

Front 114

The outer, rigid shell of the Earth above the asthenosphere. It contains the crust, continents, and plates.

Back 114

Lithosphere

Front 115

Outer liquid shell of the Earth's core, probably iron with some oxygen; inner radius, 1221 kilometres, outer radius, 3480 kilometres.

Back 115

Outer core

Front 116

The odds that the size of a future earthquake will exceed some specified value.

Back 116

Probability of exceedence of a given earthquake size

Front 117

The geological period covering about 2 million years ago to the present.

Back 117

Quaternary

Front 118

Also called primary, longitudinal, irrotational, push, pressure, dilatational, compressional, or push-pull wave. They are the fastest body waves and arrive at stations before the S waves, or secondary waves.

Back 118

P wave

Front 119

The study of ancient (prehistoric) earthquakes from their geological evidences.

Back 119

Paleoseismology

Front 120

Continental margin formed during initial rifting apart of continents to form an ocean; frequently has thick sedimentary deposits.

Back 120

Passive margin

Front 121

The time interval between successive crests in a sinusoidal wave train; it is the inverse of the frequency of a cyclic event.

Back 121

Period (wave)

Front 122

The onset of a displacement or oscillation on a seismogram, indicating the arrival of a different type of seismic wave.

Back 122

Phase: (seismic)

Front 123

The crust and upper mantle of the earth are made up of about a dozen large plates and several smaller ones that are constantly moving. The movements are very slow -only a few centimetres per year. Where the plates rub against one another, strain builds up, especially at the edges.

Back 123

Plates and plate tectonics

Front 124

A change in the geological or geophysical conditions that is a forerunner to earthquake generation on a fault. It cannot reliably be recognized as such beforehand.

Back 124

Precursor

Front 125

The forecasting in time, place, and magnitude of an earthquake; the forecasting of strong ground motions.

Back 125

Prediction (of earthquakes)

Front 126

The number of cases that meet a given description divided by the total number of (equally likely) cases possible.

Back 126

Probability

Front 127

A type of surface wave having a retrograde elliptical motion at the Earth's surface. These are the slowest, but often the largest and most destructive, of the wave types caused by an earthquake.

Back 127

Rayleigh wave

Front 128

It is a measure of intensity of shaking from an earthquake. This scale was replaced by the Mercalli intensity scale.

Back 128

Rossi-Forel Intensity Scale:

Front 129

The elevation of the water level above the immediate tide level when a tsunami runs up onto the coastal land.

Back 129

Runup height

Front 130

Also called shear, secondary, rotational, tangential, equivoluminal, distortional, transverse, or shake wave. These waves carry energy through the Earth in very complex patterns of transverse (crosswise) waves.

Back 130

S wave

Front 131

These waves move more slowly than P waves, but in an earthquake they are usually bigger.

Back 131

S wave

Front 132

A narrow geological depression found in strike-slip fault zones. Those that contain water are called sag ponds.

Back 132

Sag (fault)

Front 133

A cliff or steep slope formed by displacement of the ground surface.

Back 133

Scarp (fault)

Front 134

A free or standing wave oscillation of the surface of water in an enclosed basin, that is initiated by local atmospheric changes, tidal currents, or earthquakes. Similar to water sloshing in a bathtub.

Back 134

Seiche

Front 135

Of or having to do with earthquakes.

Back 135

Seismic

Front 136

An elongated earthquake zone, for example, circum-Pacific, Mediterranean, Rocky Mountain.

Back 136

Seismic belt

Front 137

About 60% of the world's earthquakes occur in the ______

Back 137

Circum-Pacific seismic belt

Front 138

They are usually felt as a rolling or rocking motion and, in the case of major earthquakes, can be seen as they approach.

Back 138

Rayleigh wave

Front 139

A surface or thin layer within the Earth across which P-wave and/or S-wave velocities change rapidly.

Back 139

Seismic discontinuity

Front 140

An area in an earthquake-prone region where there is a below-average release of seismic energy.

Back 140

Seismic gap

Front 141

A tsunami generated by an undersea earthquake.

Back 141

Seismic Sea Wave

Front 142

They are vibrations generated by sudden movements of rock. After earthquakes occur, they propagate from the hypocentre to the surface of the Earth.

Back 142

Seismic Wave

Front 143

A region in which earthquakes are known to occur.

Back 143

Seismic Zone

Front 144

The occurrence of earthquakes in space and time.

Back 144

Seismicity:

Front 145

Recording of ground motions made by a seismograph.

Back 145

Seismogram

Front 146

A very sensitive instrument used to record and measure earthquakes.

Back 146

Seismograph

Front 147

A scientist who studies earthquakes, seismic sources, and wave propagation through the Earth.

Back 147

Seismologist

Front 148

The study of earthquakes, seismic sources, and wave propagation through the Earth.

Back 148

Seismology

Front 149

The approximate length of time between earthquakes in a specific seismically active area.

Back 149

Recurrence Interval

Front 150

The sensor part of the seismograph, usually a suspended pendulum.

Back 150

Seismometer

Front 151

The instrumental aspects of seismology.

Back 151

Seismometry

Front 152

A simple seismograph recording on a plate without time marks.

Back 152

Seismoscope

Front 153

The study of earthquakes and their relationships with faults.

Back 153

Seismotectonics

Front 154

The area on the Earth's surface protected from seismic wave arrivals.

Back 154

Shadow zone

Front 155

The comparison between the amplitude of the seismic signal and the amplitude of noise caused by seismic unrest and (or) the seismic instruments.

Back 155

Signal-to-noise ratio

Front 156

The relative motion of one face of a fault relative to the other.

Back 156

Slip (fault)

Front 157

Growth in the amplitude of earthquakes when seismic waves pass from rock into less rigid material such as soil.

Back 157

Soil amplification

Front 158

The layout of seismometer or geophone groups from which data from a single shot (the explosive charge) are recorded simultaneously.

Back 158

Spread

Front 159

To bounce back from a surface that represents an acoustic impedance contrast.

Back 159

Reflect

Front 160

To bend or change direction due to an acoustic impedance contrast.

Back 160

Refract

Front 161

The rock above the fault plane (the "hanging"wall) moves up and over the rock below ("foot" wall).

Back 161

Reverse faulting

Front 162

Region where the crust has split apart, usually marked by a rift valley (e.g., East African Rift, Rhine Graben).

Back 162

Rift

Front 163

A strike-slip fault on which the displacement of the far block is to the right when viewed from either side. The Queen Charlotte fault is one of this type of fault.

Back 163

Right-lateral fault: (dextral)

Front 164

An index of the resistance of an elastic body to shear. The ratio of the shearing stress to the amount of angular rotation it produces in a rock sample.

Back 164

Rigidity

Front 165

The probabilistic risk is the odds of an earthquake occurring and causing damage within a given time interval and region.

Back 165

Risk (seismic)

Front 166

The geometrical deformation or change in shape of a body. The change in an angle, length, area, or volume divided by the original value.

Back 166

Strain (elastic)

Front 167

Earthquakes resulting from sudden release of energy stored by major deformation of the Earth.

Back 167

Tectonic earthquakes

Front 168

An earthquake that is distant (usually more than 20 degrees) from the recording station.

Back 168

Teleseism

Front 169

A reverse fault in which the upper rocks above the fault plane move up and over the lower rocks at an angle of 30 ° or less so that older strata are placed over younger.

Back 169

Thrust fault

Front 170

Construction of the image of velocity variations inside the Earth from measurements of seismic waves at the surface.

Back 170

Tomography

Front 171

A strike-slip fault connecting the ends of an offset in a midoceanic ridge, an island arc, or an arc­ridge chain. Pairs of plates slide past each other along these.

Back 171

Transform fault

Front 172

The time required for a wave train to travel from its source to the point of observation.

Back 172

Travel time

Front 173

A graph of travel time versus distance for the arrival of seismic waves from distant events. Each type of seismic wave has its own curve.

Back 173

Travel-time curve

Front 174

Long, narrow arcuate depression in the seabed which results from the bending of the lithospheric plate as it descends into the mantle at a subduction zone.

Back 174

Trench

Front 175

The point where three plates meet.

Back 175

Triple junction

Front 176

A series of huge ocean waves caused by a rapid, large-scale disturbance of the sea water, such as a major earthquake beneath the seabed that causes large vertical movements.

Back 176

Tsunami

Front 177

The sudden reduction of stress across the fault plane during rupture.

Back 177

Stress (drop)

Front 178

Loosely arranged, not cemented together, so particles separate easily.

Back 178

Unconsolidated

Front 179

UTC

Back 179

Coordinated Universal Time

Front 180

The time scale based on the atomic second but corrected every now and again to keep it in approximate sync with the earth's rotation.

Back 180

UTC

Front 181

A material which can behave as an elastic solid on a short time scale and as a viscous fluid on a long time scale.

Back 181

Viscoelastic material

Front 182

An opening in the crust that has allowed magma to reach the surface.

Back 182

Volcano

Front 183

Geological process which involved the eruption of molten rock.

Back 183

Volcanism

Front 184

Imaginary surface or line that joins points at which the waves from a source are in phase (e.g., all at a maximum or all at a minimum).

Back 184

Wavefront

Front 185

The distance between two successive crests or troughs of a wave.

Back 185

Wavelength

Front 186

A measure of the forces acting on a body in units of force per unit area.

Back 186

Stress (elastic)

Front 187

The line of intersection between the fault plane and the surface of the Earth. Its orientation is expressed as the angle west or east of true north.

Back 187

Strike of fault

Front 188

A fault whose relative displacement is purely horizontal.

Back 188

Strike-slip fault

Front 189

The shaking of the ground near an earthquake source made up of potentially damaging seismic waves of various types.

Back 189

Strong ground motion

Front 190

A region where the earth's plates collide, with one plate sliding beneath the other. The world's largest earthquakes occur along this type of plate boundary.

Back 190

Subduction Zone

Front 191

Waves that move over the surface of the Earth. Rayleigh and Love waves are examples.

Back 191

Surface Waves

Front 192

Magnitude of an earthquake estimated from measurements of the amplitude of surface waves.

Back 192

Surface-wave magnitude: MS

Front 193

A series of minor earthquakes, none of which may be identified as the main shock, occurring in a limited area and time.

Back 193

Swarm: (or Earthquake swarm)

Front 194

The geometrical deformation or change in shape of a body. The change in an angle, length, area, or volume divided by the original value.

Back 194

Strain (elastic)

Front 195

Earthquakes resulting from sudden release of energy stored by major deformation of the Earth.

Back 195

Tectonic earthquakes

Front 196

An earthquake that is distant (usually more than 20 degrees) from the recording station.

Back 196

Teleseism

Front 197

A reverse fault in which the upper rocks above the fault plane move up and over the lower rocks at an angle of 30 ° or less so that older strata are placed over younger.

Back 197

Thrust fault

Front 198

Construction of the image of velocity variations inside the Earth from measurements of seismic waves at the surface.

Back 198

Tomography

Front 199

A strike-slip fault connecting the ends of an offset in a midoceanic ridge, an island arc, or an arc­ridge chain. Pairs of plates slide past each other along these.

Back 199

Transform fault

Front 200

The time required for a wave train to travel from its source to the point of observation.

Back 200

Travel time

Front 201

A graph of travel time versus distance for the arrival of seismic waves from distant events. Each type of seismic wave has its own curve.

Back 201

Travel-time curve

Front 202

Long, narrow arcuate depression in the seabed which results from the bending of the lithospheric plate as it descends into the mantle at a subduction zone.

Back 202

Trench

Front 203

The point where three plates meet.

Back 203

Triple junction

Front 204

A series of huge ocean waves caused by a rapid, large-scale disturbance of the sea water, such as a major earthquake beneath the seabed that causes large vertical movements.

Back 204

Tsunami

Front 205

The sudden reduction of stress across the fault plane during rupture.

Back 205

Stress (drop)

Front 206

Loosely arranged, not cemented together, so particles separate easily.

Back 206

Unconsolidated

Front 207

UTC

Back 207

Coordinated Universal Time

Front 208

The time scale based on the atomic second but corrected every now and again to keep it in approximate sync with the earth's rotation.

Back 208

UTC

Front 209

A material which can behave as an elastic solid on a short time scale and as a viscous fluid on a long time scale.

Back 209

Viscoelastic material

Front 210

An opening in the crust that has allowed magma to reach the surface.

Back 210

Volcano

Front 211

Geological process which involved the eruption of molten rock.

Back 211

Volcanism

Front 212

Imaginary surface or line that joins points at which the waves from a source are in phase (e.g., all at a maximum or all at a minimum).

Back 212

Wavefront

Front 213

The distance between two successive crests or troughs of a wave.

Back 213

Wavelength

Front 214

In the Philippines, the intensity of an earthquake is determined using the _____

Back 214

PHIVOLCS Earthquake Intensity Scale (PEIS)

Front 215

Types of Earthquakes

Back 215

Tectonic Earthquakes

Volcanic Earthquakes

Man-made Earthquakes

Front 216

A measure of the forces acting on a body in units of force per unit area.

Back 216

Stress (elastic)

Front 217

Produced by sudden movement along faults and plate boundaries.

Back 217

Tectonic earthquakes

Front 218

Induced by rising lava or magma beneath active volcanoes.

Back 218

Volcanic earthquakes

Front 219

Induced by mining and extraction of natural resources from the ground and other human activities like, large dam and building construction, atomic explosions, etc.

Back 219

Man-made earthquakes

Front 220

The line of intersection between the fault plane and the surface of the Earth. Its orientation is expressed as the angle west or east of true north.

Back 220

Strike of fault

Front 221

A fault whose relative displacement is purely horizontal.

Back 221

Strike-slip fault

Front 222

The shaking of the ground near an earthquake source made up of potentially damaging seismic waves of various types.

Back 222

Strong ground motion

Front 223

A region where the earth's plates collide, with one plate sliding beneath the other. The world's largest earthquakes occur along this type of plate boundary.

Back 223

Subduction Zone

Front 224

Waves that move over the surface of the Earth. Rayleigh and Love waves are examples.

Back 224

Surface Waves

Front 225

Magnitude of an earthquake estimated from measurements of the amplitude of surface waves.

Back 225

Surface-wave magnitude: MS

Front 226

A series of minor earthquakes, none of which may be identified as the main shock, occurring in a limited area and time.

Back 226

Swarm: (or Earthquake swarm)

Front 227

The geometrical deformation or change in shape of a body. The change in an angle, length, area, or volume divided by the original value.

Back 227

Strain (elastic)

Front 228

Earthquakes resulting from sudden release of energy stored by major deformation of the Earth.

Back 228

Tectonic earthquakes

Front 229

An earthquake that is distant (usually more than 20 degrees) from the recording station.

Back 229

Teleseism

Front 230

A reverse fault in which the upper rocks above the fault plane move up and over the lower rocks at an angle of 30 ° or less so that older strata are placed over younger.

Back 230

Thrust fault

Front 231

Construction of the image of velocity variations inside the Earth from measurements of seismic waves at the surface.

Back 231

Tomography

Front 232

A strike-slip fault connecting the ends of an offset in a midoceanic ridge, an island arc, or an arc­ridge chain. Pairs of plates slide past each other along these.

Back 232

Transform fault

Front 233

The time required for a wave train to travel from its source to the point of observation.

Back 233

Travel time

Front 234

A graph of travel time versus distance for the arrival of seismic waves from distant events. Each type of seismic wave has its own curve.

Back 234

Travel-time curve

Front 235

Long, narrow arcuate depression in the seabed which results from the bending of the lithospheric plate as it descends into the mantle at a subduction zone.

Back 235

Trench

Front 236

The point where three plates meet.

Back 236

Triple junction

Front 237

A series of huge ocean waves caused by a rapid, large-scale disturbance of the sea water, such as a major earthquake beneath the seabed that causes large vertical movements.

Back 237

Tsunami

Front 238

The sudden reduction of stress across the fault plane during rupture.

Back 238

Stress (drop)

Front 239

Loosely arranged, not cemented together, so particles separate easily.

Back 239

Unconsolidated

Front 240

UTC

Back 240

Coordinated Universal Time

Front 241

The time scale based on the atomic second but corrected every now and again to keep it in approximate sync with the earth's rotation.

Back 241

UTC

Front 242

A material which can behave as an elastic solid on a short time scale and as a viscous fluid on a long time scale.

Back 242

Viscoelastic material

Front 243

An opening in the crust that has allowed magma to reach the surface.

Back 243

Volcano

Front 244

Geological process which involved the eruption of molten rock.

Back 244

Volcanism

Front 245

Imaginary surface or line that joins points at which the waves from a source are in phase (e.g., all at a maximum or all at a minimum).

Back 245

Wavefront

Front 246

The distance between two successive crests or troughs of a wave.

Back 246

Wavelength

Front 247

In the Philippines, the intensity of an earthquake is determined using the _____

Back 247

PHIVOLCS Earthquake Intensity Scale (PEIS)

Front 248

Types of Earthquakes

Back 248

Tectonic Earthquakes

Volcanic Earthquakes

Man-made Earthquakes

Front 249

A measure of the forces acting on a body in units of force per unit area.

Back 249

Stress (elastic)

Front 250

Produced by sudden movement along faults and plate boundaries.

Back 250

Tectonic earthquakes

Front 251

Induced by rising lava or magma beneath active volcanoes.

Back 251

Volcanic earthquakes

Front 252

Induced by mining and extraction of natural resources from the ground and other human activities like, large dam and building construction, atomic explosions, etc.

Back 252

Man-made earthquakes

Front 253

The line of intersection between the fault plane and the surface of the Earth. Its orientation is expressed as the angle west or east of true north.

Back 253

Strike of fault

Front 254

A fault whose relative displacement is purely horizontal.

Back 254

Strike-slip fault

Front 255

The shaking of the ground near an earthquake source made up of potentially damaging seismic waves of various types.

Back 255

Strong ground motion

Front 256

A region where the earth's plates collide, with one plate sliding beneath the other. The world's largest earthquakes occur along this type of plate boundary.

Back 256

Subduction Zone

Front 257

Waves that move over the surface of the Earth. Rayleigh and Love waves are examples.

Back 257

Surface Waves

Front 258

Magnitude of an earthquake estimated from measurements of the amplitude of surface waves.

Back 258

Surface-wave magnitude: MS

Front 259

A series of minor earthquakes, none of which may be identified as the main shock, occurring in a limited area and time.

Back 259

Swarm: (or Earthquake swarm)