Ground Motion Characteristics Questions and Answers

Answer: A

Correct answer: 1, 2 and 3

All three are correct and together they explain why three amplitude parameters are needed rather than one. Differentiation emphasises high frequencies and integration emphasises low ones, so acceleration is dominated by the high end of the spectrum, displacement by the low end, and velocity by the intermediate range in between.

Answer: B

The earthquake itself sets what is radiated, the travel path filters and attenuates it, and the local ground modifies it again before it reaches the foundation. Separating the three is the basis of every ground motion prediction equation.

Answer: C

Correct answer: magnitude, distance and site conditions

A ground motion prediction equation is a regression fitted to recorded data, expressing a parameter such as peak acceleration or a spectral ordinate as a function of magnitude, source-to-site distance and a site classification, often with terms for style of faulting and for near-fault effects. It is the engine of hazard analysis, converting a postulated earthquake into an expected motion.

Answer: D

The slower material carries the same energy at larger amplitude, and the layer resonates at its own longer period. Very soft deep deposits can nonetheless limit the peak acceleration by yielding, while still amplifying long-period motion.

Answer: A

The old lake bed amplified motion strongly near two seconds, and buildings of about that natural period were destroyed while shorter and taller ones survived. The source was hundreds of kilometres away, which makes the site effect unmistakable.

Answer: B

Correct answer: at ridge crests than at the base of a slope

Waves arriving at a ridge are focused by its geometry and are reflected within it, so the crest shakes more strongly than the surrounding ground - sometimes by a factor of two or more. The effect is well documented in post-earthquake damage surveys, where structures on ridge lines fare noticeably worse than identical ones on the flat.

Answer: C

Energy entering through the edges is repeatedly reflected inside the soft fill, lengthening the duration and amplifying long periods well beyond what a flat layered model predicts. Basin-edge focusing has been implicated in concentrated damage bands.

Answer: D

Close to the rupture the motion can contain one strong pulse that demands a large displacement in a single excursion, which is severe for structures and for isolation systems. Far-field motions are more nearly random and longer.

Answer: A

Correct answer: permanent ground displacement from the fault slip

Fling step is the static offset the ground acquires because the fault has moved: it appears in a near-fault record as a one-sided pulse in the velocity trace and a permanent step in the displacement. It is distinct from forward directivity, which is a large but transient pulse, and both are near-fault phenomena absent at distance.

Answer: B

Correct answer: a fraction of the horizontal component

Vertical motion is conventionally taken as about two thirds of the horizontal, a ratio that holds reasonably well away from the immediate vicinity of the fault. Close to the source the vertical component can approach or exceed the horizontal, which is why near-fault design treats it separately. It matters most for long cantilevers and prestressed members.