What is the seismic gap hypothesis?

Answered by Douglas Hiatt

The seismic gap hypothesis is a theory that suggests that the likelihood of an earthquake occurring increases over time in areas where there has not been a significant earthquake for a while. This hypothesis is based on the idea that strain accumulates along faults or plate boundaries, and when this accumulated strain is released through an earthquake, it reduces the potential for future earthquakes in that area.

The concept of seismic gaps was first introduced by McCann et al., who observed that certain faults or plate boundaries appeared to have sections that had not experienced a major earthquake for a long time. These sections were termed “seismic gaps” and were believed to represent areas of increased earthquake hazard.

The idea behind the seismic gap hypothesis is that as time passes without a significant earthquake in a seismic gap, the strain along the fault or plate boundary continues to accumulate. Eventually, the accumulated strain becomes so great that it overwhelms the strength of the rocks, leading to the occurrence of a large earthquake.

The seismic gap theory has been supported by numerous studies and observations. For example, historical records have shown that areas with long periods of seismic quiescence often experience large earthquakes when the accumulated strain is finally released. Additionally, geological and geodetic measurements have provided evidence of strain accumulation in seismic gaps.

One of the strengths of the seismic gap hypothesis is that it provides a means of earthquake forecasting by identifying areas that are more likely to experience a significant earthquake in the future. By monitoring the strain accumulation in seismic gaps, scientists can assess the potential for future earthquakes and implement appropriate mitigation measures in areas at higher risk.

However, it is important to note that the seismic gap hypothesis is not without limitations. Predicting when and where an earthquake will occur is still a challenging task, and the seismic gap theory does not provide precise information about the timing or magnitude of future earthquakes. Additionally, not all earthquakes occur in seismic gaps, and some earthquakes may occur in areas that were not previously identified as having a high earthquake hazard.

The seismic gap hypothesis suggests that earthquake hazard increases with time since the last significant earthquake in certain faults or plate boundaries. It is based on the idea that strain accumulates along these features, and when the accumulated strain exceeds the strength of the rocks, a large earthquake occurs. While the seismic gap theory has provided valuable insights into earthquake forecasting, it is not a foolproof method and has its limitations.