“Understanding Earthquake Intensity: Factors That Influence How You Feel the Shake”

On Monday afternoon, a 4.4-magnitude earthquake struck the Los Angeles area, causing significant shaking and rattling for Angelenos. However, the magnitude of an earthquake only tells part of the story. According to Richard Allen, the director of the University of California, Berkeley Seismology Lab, various factors influence how strongly an earthquake is felt on the Earth’s surface.

Magnitude is a measurement of an earthquake’s strength, typically expressed using the Richter Scale. Larger and longer-lasting earthquakes have higher magnitudes compared to smaller, shorter ones. Proximity to the epicenter of an earthquake plays a significant role in how intensely it is felt. The closer one is to the epicenter, the more intense the shaking will be.

For higher magnitude earthquakes, the most intense shaking is often felt along the fault line where the earthquake occurs. This means that two individuals equidistant from the epicenter may experience different intensities of shaking if only one of them is along the fault line. The type of building structure also matters during an earthquake. One- or two-story buildings amplify seismic shaking slightly, while taller buildings and skyscrapers absorb more of the quake’s energy and can sway back and forth.

The composition of the soil and rocks beneath an area can also affect the intensity of an earthquake. People living in sedimentary basins with soft soils experience more powerful shaking as the soil amplifies seismic waves. On the other hand, those on harder rocky surfaces may feel a weaker quake. Soft soils can cause earthquakes to last longer by trapping energy and increasing the duration of tremors.

The waves generated by an earthquake can also feel different. P waves, the first waves to emanate from an earthquake, are often high-frequency and result in jerky shaking. S waves, which come later, produce more gradual oscillations, creating a rolling sensation. People close to the epicenter typically feel the more intense P waves, while those further away may only feel the slower-traveling S waves.

Understanding these factors can help individuals better prepare for and respond to earthquakes, ensuring their safety and well-being during seismic events.