The key difference between epicenter and hypocenter is that epicenter is the point that exists directly above the hypocenter whereas hypocenter is the point at which an earthquake or an underground explosion originates.
Epicenter and hypocenter are two important terms in the field of seismology, especially in describing earthquakes and underground explosions.
CONTENTS
1. Overview and Key Difference
2. What is Epicenter
3. What is Hypocenter
4. Side by Side Comparison – Epicenter vs Hypocenter in Tabular Form
5. Summary
What is an Epicenter?
Epicenter is the point on the Earth’s surface which exists directly above the point from which an earthquake or an underground explosion originates. The point from which the earthquake or underground explosion originates is known as the hypocenter (also named as “focus”).
Usually, during an earthquake, the point where the greatest damage takes place is the epicenter. However, the length of the subsurface fault rupture can be a long damage, and its damage can spread on the surface across the entire rupture zone.
The term fault rupture refers to the damage that occurs beginning from the “focus” and then expanding along the fault surface. The term “focus” is the point at which fault slipping begins. The fault rupture may stop when the stresses become insufficient to continue breaking the fault or when the rupture enters ductile material.
Figure 01: Epicenter and Hypocenter in a Simple Diagram
We can observe seismic waves during an earthquake propagating in all directions from the hypocenter. However, seismic shadowing occurs on the opposite side of the Earth with respect to the epicenter. This happens because the planet’s liquid outer core refracts the longitudinal or compressional and it absorbs the transverse or shear waves. The term epicentral distance refers to the distance from epicenter to any interested point. This distance is measured using the unit “degrees”.
The term “epicenter” comes from the Latin noun “epicentrum” meaning “occupying a cardinal point, situated on a center”. This term was introduced by Robert Mallet, a seismologist from Italy. In addition, this term is useful in referring to “the center of activity”.
What is Hypocenter?
Hypocenter is the point at which an earthquake or an underground explosion originates. This term is synonymous with the term “focus” in seismology. We can also use this term to refer to the term “ground zero”, which is the point that is directly beneath a nuclear airburst.
Hypocenter is the point at which the strain energy stored in the rock is first released. This marks the point where the fault begins to rupture. The rupture occurs directly beneath the epicenter. The distance between the epicenter and the hypocenter is named as the focal or hypocentral depth.
We can easily calculate the hypocentral depth depending on the seismic wave phenomena. However, this measurement has uncertainty as with all the wave phenomena calculations in physics. This is because in such measurements, uncertainty grows with the wavelength. Therefore, the focal depth of the source of the low-frequency waves is difficult to determine exactly.
What is the Difference Between Epicenter and Hypocenter?
Epicenter and hypocenter are two important terms in the field of seismology, especially in describing earthquakes and underground explosions. The key difference between epicenter and hypocenter is that epicenter is the point that exists directly above the hypocenter whereas hypocenter is the point at which an earthquake or an underground explosion originates. Furthermore, during an earthquake, most of the damage occurs at the epicenter while the rupture of the Earth’s surface begins at hypocenter.
Below is a summary of the difference between epicenter and hypocenter in tabular form.
Summary – Epicenter vs Hypocenter
Epicenter and hypocenter are two important terms in the field of seismology, especially in describing earthquakes and underground explosions. The key difference between epicenter and hypocenter is that epicenter is the point that exists directly above the hypocenter whereas hypocenter is the point at which an earthquake or an underground explosion originates.
Reference:
1. “Earthquake Hypocenter.” ScienceDirect, Available here.
Image Courtesy:
1. “Epicenter Diagram” By AnsateSam Hocevar (original author; this is a derivative work)User:TFerenczy create SVG version; cs translationUser:NikNaks es translationUser:Lies Van Rompaey nl translationUser:Rostik252004 ru translationUser:Ата uk translation – Epicenter.png: (CC BY-SA 1.0) via Commons Wikimedia