Question

Click “Next” and describe the following:

i. Under Faults describe Hypocenter:


ii. Under Faults describe Epicenter:


iii. Seismograph:


iv. Richter Scale:


v. Ring of Fire:

Answer 1

i. Hypocenter (focus)
- The point inside the Earth where rupture of a fault and the initial release of seismic energy occur.
- Has depth and coordinates (latitude, longitude, depth).
- Seismic waves radiate outward from the hypocenter; depth influences shaking intensity at the surface.

ii. Epicenter
- The point on the Earth’s surface directly above the hypocenter.
- Used as the surface location reference for an earthquake; reported in maps and news.
- Not always where the strongest damage occurs (that depends on depth, local geology, and fault rupture extent).

iii. Seismograph
- An instrument that detects and records ground motion caused by seismic waves.
- Consists of a sensor (seismometer) and a recorder; output is a seismogram showing wave arrivals (P, S, surface waves).
- Seismograms are used to determine earthquake time, magnitude, and to locate the hypocenter/epicenter.

iv. Richter Scale
- Originally the local magnitude scale (ML) developed by Charles Richter in 1935 to quantify earthquake size from recorded wave amplitudes.
- Logarithmic: each whole-number increase ≈ 10× greater ground-amplitude and about 31.6× more energy release.
- Widely known but largely replaced for large quakes by moment magnitude (Mw), which more accurately represents total energy for big events.

v. Ring of Fire
- A horseshoe-shaped zone around the edges of the Pacific Ocean characterized by frequent earthquakes and many active volcanoes.
- Caused mainly by subduction and other plate boundary interactions along the Pacific Plate and adjacent plates.
- Responsible for a large proportion of the world’s seismic and volcanic activity (roughly 75% of active volcanoes and about 90% of earthquakes).