Natural Hazards
Comparing Shaking Intensity from Two Bay Area Earthquakes
The 1989 Loma Prieta earthquake caused billions of dollars in damage and claimed more than sixty lives. But was it "the big one"? Take a look at the comparison between the images below for the 1989 Loma Prieta and the 1906 San Francisco earthquakes, and decide for yourself.
The colors on the map indicate Modified Mercalli Shaking Intensity (MMI) at each point, which is usually (but not...
Seismographs - Keeping Track of Earthquakes
Throw a rock into a pond or lake and watch the waves rippling out in all directions from the point of impact. Just as this impact sets waves in motion on a quiet pond, so an earthquake generates seismic waves that radiate out through the Earth.
Seismic Seiches
Definition of seismic seiches and examples dating back to their first public mention in 1755.
Recommended Reading for the Changing Earth
Recommended titles for the Changing Earth for both adults and kids.
Introduction to Paleoseismology
Paleoseismology and the Hayward Fault
A large, widely damaging earthquake will occur on the Hayward fault in the future. That much we know.
What we don't know is when.
How Seismic Waves Affect Different Size Buildings
Groundwater Effects from Earthquakes
Note: Some of the explanations below are speculative and should not be relied upon for decision-making. Please see the reference articles (below) for published results.
Seismic waves have two main types of effects on groundwater levels: oscillations, and "permanent" offsets. Muddy or turbid water at long distances from...
Focal Mechanisms... or "Beachballs"
This page explains the concept of focal mechanisms, commonly referred to as "beachballs".
Earthquake Magnitude, Energy Release, and Shaking Intensity
Earthquake magnitude, energy release, and shaking intensity are all related measurements of an earthquake that are often confused with one another. Their dependencies and relationships can be complicated, and even one of these concepts alone can be confusing.
Here we'll look at each of these, as well as their interconnectedness and dependencies.