# Intensity Measure Relationship (IMR)

An **Intensity Measure Relationship (IMR)** is one of the two main modeling components in OpenSHA, the other being an Earthquake Rupture Forecast (ERF).

An **IMR** gives the probability of exceeding some Intensity Measure Level (IML) of a specified Intensity Measure Type (IMT) given a Site of interest and an Earthquake Rupture.

Note that no presumptions are made with respect to how probabilities are computed, leaving the possibility of using full waveform modeling from first principles of physics. At present most IMRs implemented in OpenSHA constitute empirical Attenuation Relationships, although waveform modeling is being implemented in collaboration with the SCEC CyberShake project. See the figure at right for information on other potential types of IMRs.