CE442 Geotechnical Earthquake Engineering

Study Notes

Earthquake engineering aims to mitigate the impacts of earthquakes on people and their environment.
It combines aspects of geology, seismology, geotechnical engineering, structural engineering, risk analysis, and other technical fields.
Hundreds of millions of people worldwide live with significant earthquake risk, posing an economic threat to local, regional, and national economies.

Earthquake records date back 3000 years in China, 1600 years in Japan and the Eastern Mediterranean, and 350 years in the United States.
Human experience with earthquakes is brief compared to the millions of years over which earthquakes have occurred.
Earthquakes cannot be prevented, but the goal is to mitigate their effects to reduce loss of life, injuries, and damage.

Structural damage: harm inflicted on buildings, bridges, roads, and other infrastructure due to the forces generated by an earthquake.
Liquefaction: a process that causes soft, young, water-saturated, fine-grained sands and silts to behave like viscous fluids, leading to ground failure.

Building codes: seismic design requirements have continuously improved, incorporating lessons from past earthquakes.
Strength and ductility: modern design practices emphasize not only structural strength but also ductility, allowing buildings to withstand and absorb seismic energy.
Geotechnical role: accurate prediction of ground motions is crucial for earthquake-resistant design, with geotechnical earthquake engineers providing essential data for structural engineers.

Occurs when an earthquake causes water-saturated, fine-grained soils to lose their strength and behave like a liquid.
Can lead to ground failure, causing damage to buildings and infrastructure.

1556 Shaanxi Earthquake (China): the deadliest earthquake in recorded history, with an estimated death toll of 530,000.
Various earthquakes in the Philippines, including the Ragay Gulf Earthquake (1973), Casiguran Earthquake (1968), and others.

Deals with the design and construction of projects to resist the effects of earthquakes.
Requires an understanding of geology, seismology, and earthquake engineering.
Activities performed by geotechnical engineers include:
- Investigating the possibility of liquefaction at the site.
- Calculating the settlement of the structure caused by the anticipated earthquake.
- Checking foundation design parameters to ensure the foundation does not fail during the anticipated earthquake.

Earthquake is manifested as ground shaking caused by sudden release of energy in the Earth's crust.
Can originate from different sources, such as dislocations of the crust, volcanic eruptions, or man-made explosions.
Plates are large and stable rigid rock slabs with a thickness of about 100 km, forming the crust or lithosphere and part of the upper mantle of the Earth.

Divergent Boundaries: regions where two tectonic plates are moving apart from each other, resulting in the creation of new crust.
Transform Boundaries: regions where two tectonic plates slide past each other horizontally, causing earthquakes due to the build-up and release of stress along the fault lines.
Convergent Plate Boundaries: regions where two tectonic plates are moving towards each other, resulting in the formation of mountains, earthquakes, and volcanic activity.

The Earth is composed of a sequence of shells or layers called geospheres, including the lithosphere, asthenosphere, outer core, and inner core.
Lithosphere: the thinnest outer solid shell, 200 km thick with a density of 1500 kg/m3.
Asthenosphere: the mantle, 2685 km thick, surrounding the core, composed of hot, dense ultrabasic igneous rock in a plastic state.
Outer Core: a molten layer of iron and nickel beneath the mantle, extending from 2,900 km to 5,150 km depth.
Inner Core: a solid, dense region at the center of the Earth, extending from 5,150 km to the core at 6,371 km depth, composed of solid iron and nickel.