WorksheetsIntroduction to Earthquake Measurement
Total questions: 10
Worksheet time: 3mins
A city reports strong shaking and structural damage in multiple neighborhoods, while instruments at a regional station record a single numeric value for the event. Which statement best distinguishes the two measurements described?
Intensity is the unique energy release of the whole quake
Magnitude lists building damage neighborhood by neighborhood
Intensity maps local effects varying by location
Magnitude compares damages across several nearby cities
Intensity is instrument-only and globally unique value
You are tasked with planning a monitoring network for a tectonically active region. Which choice best explains why seismometers are essential for determining earthquake magnitude rather than relying on eyewitness damage reports?
Seismometers only describe local shaking variations
Eyewitness accounts ensure uniform regional coverage
Reports capture fracturing plates and fault geometry
Instruments quantify whole-event energy consistently
Damage reports provide precise global unique values
An engineer must compare two nearby towns after an earthquake: Town A reports dishes and windows disturbed with minor breakage, while Town B reports heavy furniture moved and some building damage possible. Which classification best matches Town B on the Modified Mercalli Intensity scale, and why is this scale appropriate for this comparison?
Strong, because it rates shaking by objective instruments
Moderate, because it focuses on peak ground acceleration
Light, because it records qualitative human observations
Very strong, because it reflects observed structural impacts
You are tasked with planning post-event inspections. The only available data are community reports: some chimneys fell, doors overturned, and considerable building damage occurred in several blocks. Which planning priority is most justified and which intensity range does the evidence suggest?
Moderate priority; intensity around strong
Low priority; intensity likely weak to light
Instrument-based priority; intensity defined by PGA
High priority; intensity severe to violent
A field team reports: many awakened at night, some dishes and windows broken, unstable objects overturned, and disturbance of trees and poles. Which Modified Mercalli Intensity level best fits these observations?
IV: Felt indoors by many; creaking walls, slight rocking
V: Felt by nearly everyone; some breakage and overturning
VI: Felt by all; heavy furniture moved; slight damage
VII: Everybody runs outdoors; moderate damage in ordinary buildings
You are assessing two neighborhoods: one with well-designed ordinary buildings showing slight to moderate damage, and another with poorly built structures showing considerable damage. Which MMI level most consistently explains both patterns?
VI: Frightened crowds; a few fallen plaster and chimneys
IX: Buildings shifted off foundations; ground cracks visible
VII: Negligible damage in good design; moderate in ordinary
VIII: Considerable in substantial buildings; partial collapse
During an earthquake, inspectors find panel walls thrown out of frame structures, heavy furniture overturned, changes in well water, and drivers report being disturbed. What is the most probable MMI level?
VI: Some heavy furniture moved; damage slight
VII: Some chimneys broken; noticed by drivers
IX: Ground cracked conspicuously; underground pipes broken
VIII: Panel walls thrown out; heavy furniture overturned
Using the diagram, decide which statement best explains why two towns at equal distance from an earthquake’s focus reported different felt strength, even though seismographs recorded the same energy release.
Magnitude varies between towns despite identical seismograms
Seismographs measure intensity felt by nearby populations
Intensity depends on local conditions and epicenter proximity
Energy release changes as waves travel through the crust
A mid-rise building sits on loose, water-saturated sand in a seismically active area. During an M5.0 earthquake, strong shaking begins. Which mitigation plan best reduces the risk of tilt or collapse from soil failure beneath the building?
Use wider shallow footings to spread loads on surface
Install deep piles to competent strata below liquefiable layers
Add heavy superstructure mass to resist overturning
Drain site water only after an earthquake occurs
Rely on shear walls without changing the foundation
A building designed with a base isolation system experiences an earthquake. How does this system primarily help in reducing structural damage during seismic events?
By increasing the building's mass to resist shaking
By using materials that absorb seismic energy effectively
By allowing the building to move independently from ground motion
By enhancing the stiffness of the structure to prevent deformation
