Earthquake Flashcards Preview


Flashcards in Earthquake Deck (25):

is the shaking of the surface of the Earth, resulting from the sudden release of energy in the Earth's crust that creates seismic waves.



can be violent enough to toss people around and destroy whole cities. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.



is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,000 years.

Active Fault Line


It is the total energy released at the earthquake’s point of origin which is below the earth's surface.



Is the perceived strength of an earthquake based on the relative effect to people and structures on the earth’s surface.



Perceptible to people under favorable circumstances. Delicately
balanced objects are disturbed slightly. Still water in containers oscillates slowly.

I. Scarcely Perceptible


Felt by few individuals at rest indoors. Hanging objects swing slightly. Still
water in containers oscillates noticeably

II. Slightly Felt


Felt by many people indoors especially in upper floors of buildings. Vibration is felt
like the passing of a light truck. Dizziness and nausea are experienced by some people.
Hanging objects swing moderately Still water in containers oscillates moderately

III. Weak


Felt generally by people indoors and by some people outdoors. Light
sleepers are awakened. Vibration is felt like the passing of a heavy truck. Hanging objects
swing considerably. Dinner plates. glasses, windows. and doors rattle. Floors and walls of wood-
framed buildings creak. Standing motor cars may rock slightly Liquids in containers are slightly
disturbed. Water in containers oscillates strongly. Rumbling sound may sometimes be heard.

IV. Moderately Strong


Generally felt by most people indoors and outdoors. Many sleeping people are
awakened. Some are frightened, some run outdoors. Strong shaking and rocking felt throughout
buildings. Hanging objects swing violently. Dining utensils clatter and clink; some are broken.
Small. light. and unstable objects may fall or overturn. Liquids spill from filled open containers.
Standing vehicles rock noticeably Shaking of leaves and twigs of trees are noticeable.

V. Strong


Many people are frightened; many run outdoors. Some people lose their
balance. Motorists feel like driving in flat tires. Heavy objects or furniture move or may be
shifted. Small church bells may ring. Wall plaster may crack. Very old or poorly-built houses
and man-made structures are slightly damaged though well-built structures are not affected.
Limited rockfalls and rolling boulders occur in hilly to mountainous areas and escarpments.
Trees are noticeably shaken.

VI. Very Strong


Most people are frightened and run outdoors. People find it difficult to stand in
upper floors. Heavy objects and furniture overturn or topple. Big church bells may ring. Old
or poorly-built structures suffer considerable damage. Some well-built structures are slightly
damaged. Some cracks may appear on dikes, fish ponds. road surface, or concrete hollow
block walls. Limited liquefaction. lateral spreading, and landslides are observed. Trees are
shaken strongly. (Liquefaction is a process by which loose saturated sand lose strength
during an earthquake and behave like liquid.)

VII. Destructive


People are panicky. People find it difficult to stand even outdoors. Many
well-built buildings are considerably damaged. Concrete dikes and foundations of bridges
are destroyed by ground settling or toppling. Railway tracks are bent or broken. Tombstones
may be displaced. twisted. or overturned. Utility posts, towers. and monuments tilt or topple.
Water and sewer pipes may be bent. twisted. or broken. Liquefaction and lateral spreading
cause man-made structure to sink. tilt. or topple. Numerous landslides and rockfalls occur in
mountainous and hilly areas. Boulders are thrown out from their positions particularly near
the epicenter. Fissures and fault rapture may be observed. Trees are violently shaken. Water
splashes or slops over dikes or banks of rivers.

VIII. Very Destructive


People are forcibly thrown to the ground. Many cry and shake with fear.
Most buildings are totally damaged. Bridges and elevated concrete structures are toppled
or destroyed. Numerous utility posts. towers. and monuments are tilted. toppled. or broken.
Water sewer pipes are bent. twisted. or broken. Landslides and liquefaction with lateral
spreadings and sandboils are widespread. The ground is distorted into undulations. Trees
are shaken very violently with some toppled or broken. Boulders are commonly thrown out.
River water splashes violently or slops over dikes and banks.

IX. Devastating


Practically all man-made structures are destroyed. Massive
landslides and liquefaction. large-scale subsidence and uplifting of land forms. and many
ground fissures are observed. Changes in river courses and destructive seiches in large
lakes occur. Many trees are toppled. broken. and uprooted.

X. Completely Devastating


Earthquake hazards

-Ground shaking
-Ground rupture
-Ground disturbance


Is caused by the passage of seismic waves beneath structures.

Ground shaking


Is the displacement of the ground due to the violent shaking of the surface.
Vertical Displacement – occurs when one side of the ground goes up or down or both.
Horizontal displacement - is a lateral movement from side to side.

Ground Rupture


occurs when one side of the ground goes up or down or both.

Vertical Displacement


is a lateral movement from side to side.

Horizontal displacement


Takes place when there is an increase in water pressure in saturated soils because of ground shaking



is a form of mass wasting that includes a wide range of ground movements, such as rockfalls, deep failure of slopes, and shallow debris flows. 



The lowering of the land surface occurs for many reasons, such as the extraction of ground water, mining, and earthquake.

Ground disturbance


Is the series of large waves resulting from the disturbance of the sea water commonly due to an earthquake.



The ______ or ______ of an area refers to the frequency, type and size of earthquakes experienced over a period of time.

seismicity or seismic activity