is a description of the relationship of time, space, strength, and frequency of earthquake occurrences within a certain region, and its understanding is the foundation of earthquake study.

(a)  

For design purposes (a)   is described by the history of hypothesized ground acceleration and is commonly expressed in terms of the response spectrum derived from that history When records are unavailable or insufficient, smoothed response spectra are devised for design purposes to characterize the ground motion.

In principle, the designers describe the ground motion in terms of two perpendicular horizontal components and a (a)   for the entire base of the structure

Earthquakes initiate several phenomena or agents, termed _____ _____ which can cause significant damage to the built environment these include fault rupture, vibratory ground motion (i e shaking), inundation (e g tsunami, seiche, dam failure), various kinds of permanent ground failure (e g liquefaction).

(a)  

Earthquake focus or (a)   is the point from which the waves first emanate. The point on the ground surface directly above the focus is called the earthquake epicenter.

(a)   are classified into two namely shallow and deep focus. earthquakes with foci from 70 to 300 kilometers deep are called intermediate focus and those below this depth are termed deep focus.

Some intermediate and deep focus earthquakes are located away from the Pacific region, in the Hindu Kush, in Romania, in the Aegean Sea, and under Spain. The (a)   (< 70 Kms depth) is the deadliest and contribute about three-quarters of the total energy released in earthquakes throughout the world.

(a)   are numerous earthquakes, usually smaller that follow most moderate to large shallow earthquakes in the ensuing hours and even in the next several months. Aftershocks are sometimes energetic enough to cause additional damage to already weakened structures.

structures. A few earthquakes are preceded by smaller (a)   from the source area, and it has been suggested that these can be used to predict the main shock.

 These are offsets of geological structure; may range in length from a few meters to many kilometers and are drawn on a geological map as continuous or broken line.

(a)  

Slow slip produces no ground shaking

(a)  

Most plotted on geological maps are now (a)  

(a)   and geophysical work show that faults seen at the surface sometimes extend to depths of tens of kilometers in the Earth’s crust

Primary interest in seismology and earthquake engineering

(a)  

Large vertical motion occurrence as shown in the figure

(a)  

(a)   one block moves vertically with respect to the other Strike slip faults the adjacent blocks move horizontally past one another.

Slip produced large earthquakes along faults

(a)  

the faster body wave. Its motion is the same as that of a sound wave, in that, as it spreads out, it alternately pushes (compresses) and pulls (dilates) the rock

(a)  

the slower body wave. As an S wave propagates, it shears the rocks sideways at right angles to the direction of travel.

(a)  

third general type of earthquake wave. Such waves correspond to ripples of water that travel across a lake.

(a)  

- Its motion is essentially the same as that of S waves that have no vertical displacement; it moves the ground side to side in a horizontal plane parallel to the Earth’s surface, but at right angles to the direction of propagation.

(a)  

. Like rolling ocean waves, the pieces of rock disturbed by a (a)   move both vertically and horizontally in a vertical plane pointed in the direction in which the waves are travelling.

The subject of source models is an area of study for (a)   , the results of which are fundamental to our understanding of the nature of ground motion.

(a)   or risk maps recommended by seismic design codes usually do not attempt to reflect geological conditions nor to take into account variations due to soil properties.

Three factors which must be considered in assessment of seismic risk of a site have been well-defined in recent times, what are these?

(a)  

Provision of a structural geologic map, Compilation of active faults in the region and the type of displacement (e.g., left-lateral, strike-slip, etc.)

(a)  

Procedures for the estimation of ground shaking parameters for optimum engineering design are still in the early stages and many are untested

(a)  

- When there is geological indication of the presence of structurally poor foundation material (such as in flood plains and filled tidelands), a field report

(a)  

(a)   is the study of earthquake waves

(a)   are tools used to capture ground motion during an earthquake. They operate as a part of a seismographic network and are buried throughout the world.

The Chinese scholar (a)   created the first "seismoscope" in the year 132 A.D. However, this just served to signal that an earthquake was taking place; it did not record earthquakes. In 1890, the first seismograph was created.

(a)   are firmly fixed to the earth's surface so that they shake along with the earth when it moves, except for the mass on the spring, which has inertia and stays there.

The (a)   shakes beneath a mass, which causes the recording device on the mass to capture the ground motion as well as the relative motion between the mass and the rest of the instrument.

Although it is frequently used interchangeably with "seismograph," a (a)   is the internal component of the seismograph, which can be a pendulum or a mass set on a spring

The (a)   is a number (written as a Roman numeral) that quantifies the magnitude of an earthquake's impact on people, property, and the surface of the earth.

It was developed in 1931 by the American seismologists Harry Wood and Frank Neumann. This scale, composed of increasing levels of intensity that range from imperceptible shaking to catastrophic destruction, is designated by Roman numerals.

(a)  

(a)   It is a measure of earthquake size and is determined from the logarithm of the maximum displacement or amplitude of the earthquake signal as seen on the seismogram, with a correction for the distance between the focus and the seismometer.

.The measurement of (a)   is based on the seismograph's maximum motion data.

was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes

(a)  

The magnitude of an earthquake is determined from the (a)   of the amplitude of waves recorded by seismographs.

(a)   is also known as the local magnitude scale, ML

The (a)   has a practical range from 0 to 9.0 (theoretically, the scale has no upper or lower limits).

a seismograph for measuring ground acceleration as a function of time.

(a)  

a fault along which slip has occurred, either in historical or Holocene or Quaternary time, or earthquake foci are located.

(a)  

roughness on the fault surface subject to slip.

(a)  

a thrust-fault deep in the crust with no or only indirect surface expression such as a fold structure.

(a)  

magnitude of an earthquake as estimated from the amplitude of body wave.

(a)  

a series of discrete numerical digits.

(a)  

the time Interval between the first and last peaks of strong ground motion above a specified amplitude.

(a)  

the point on the Earth’s surface directly above the focus (or hypocenter) of an earthquake.

(a)  

a fracture or zone of fractures in rock along which the two sides have been displaced relative to each other parallel to the fracture. The total fault off-set may range from centimeters to kilometers

(a)  

the depth of the focus below the surface of the Earth.

(a)  

a measure of ground shaking obtained from the damage done to structures built by humans, changes in the Earth’s surface, and felt reports.

(a)  

contour lines drawn to separate one level of seismic intensity from another.

(a)  

process of soil and sand behaving like a dense fluid rather than a wet solid mass during an earthquake.

(a)  

seismic surface waves with only horizontal shear motion transverse to the direction of propagation.

(a)  

a measure of earthquake size, determined by taking the  common logarithm (base 10) of the largest ground motion recorded during the arrival of a seismic wave type and applying a standard correction for distance to the epicenter.

(a)  

a measure of earthquake size related to the leverage of theforces (couples) across the area of the fault slip, equal to the rigidity of the rock times the area of faulting times the amount of slip. Dimensions are dyne-cm (or Newton-meters).

(a)  

magnitude MW of an earthquake estimated from the seismic moment.

(a)  

a large, relatively rigid segment of the Earth’s lithosphere that moves in relation to other plates over the deeper interior. (a)   meet in convergence zones and separate at divergence zones.

a geological model in which the Earth’s crust and uppermost mantle (the lithosphere) are divided into a number of more-or-less rigid segments (plates).

(a)  

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

(a)  

the primary or fastest wave traveling away from a seismic event through the rock and consisting of a train of compressions and dilatations of the material.

(a)  

eismic surface waves with ground motion only in a vertical plane containing the direction of propagation of the waves.

(a)  

the probability of life and property loss from an earthquake hazard within a given time interval and region.

(a)  

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

(a)  

the occurrence of earthquakes in space and time.

(a)  

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

(a)  

the shaking of the ground near an earthquake source made up of large amplitude seismic waves of various types.

(a)  

the secondary seismic wave, traveling more slowly than the P wave and consisting of elastic vibrations transverse to the direction of travel. It cannot propagate in a liquid.

(a)  

he sets out to explain ““masses of dislocated stone and mortar”

(a)  

Earthquakes initiate a number of phenomena or agents, termed seismic hazards , which can cause significant damage to the built environment

(a)  

result from motion between a number of large plates comprising the earth’s crust or lithosphere

(a)  

offsets of geological structure; may range in length from a few meters to many kilometers and are drawn on a geological map as continuous or broken line

(a)  

- cause the most significant damage to human lives and properties.

(a)  

may also lead to a disturbance of the tectonic plates, causing earthquakes, which are typically much smaller than earthquakes caused by non-volcanic sources.

(a)  

produced large earthquakes along faults

(a)  

in these regions, plates slide past each other

(a)  

collision zones are regions of high present day seismic activity .

(a)  

Earthquake -concentrated zones are called (a)   .

may range in length from less than a meter to many hundreds of kilometers.

(a)  

the adjacent blocks move horizontally past one another .

(a)  

(a)   can be right ‐lateral or left ‐lateral , depending on the sense of the relative motion of the blocks for an observer located on one side of the fault line . T

Most earthquakes have focal depths in the range of (a)   km, while intermediate events have foci at about 20–50 km and deep earthquakes occur at 300–700 km underground

definitions ranged from the perspective in socioeconomic effects to development as a branch of engineering with the estimation of earthquake consequences and the mitigation of these consequences (Elnashai and Sarno, 2015).

(a)  

Several scales exist, but the ones most commonly used in the United States are the Modified Mercalli scale and the (a)   . There are many intensities for an earthquake, depending on where you are, unlike the magnitude, which is one number for each earthquake

(PEIS)

(a)  

It was developed in 1931 by the American seismologists __________ and __________

(a)  

Rossi-forel scale was one of the first seismic scales to reflect earthquake intensities developed by (a)   of Italy

The rossi-forel scale was developed by (a)   of Switzerland in the late 19th century.

The Richter magnitude scale was developed in 1935 by (a)   of the California Institute of Technology as a mathematical device to compare the size of earthquake