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  2. Peak ground acceleration - Wikipedia

    en.wikipedia.org/wiki/Peak_ground_acceleration

    Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an accelerogram at a site during a particular earthquake. [ 1 ]

  3. List of free geology software - Wikipedia

    en.wikipedia.org/wiki/List_of_free_geology_software

    3D structural geological modeling CGRE Institute, RWTH Aachen - Miguel de la Varga LGPL v3: Cross-platform: Python: Open-source implicit geological modeling that allows for automation of model construction and is aimed to enable the implementation of probabilistic machine-learning methods, e.g. for uncertainty analysis.

  4. Moment magnitude scale - Wikipedia

    en.wikipedia.org/wiki/Moment_magnitude_scale

    It has become the standard scale used by seismological authorities like the United States Geological Survey [4] for reporting large earthquakes (typically M > 4), replacing the local magnitude (M L ) and surface-wave magnitude (M s ) scales. Subtypes of the moment magnitude scale (M ww , etc.) reflect different ways of estimating the seismic ...

  5. Seismic intensity scales - Wikipedia

    en.wikipedia.org/wiki/Seismic_intensity_scales

    Seismic intensity scales categorize the intensity or severity of ground shaking (quaking) at a given location, such as resulting from an earthquake.They are distinguished from seismic magnitude scales, which measure the magnitude or overall strength of an earthquake, which may, or perhaps may not, cause perceptible shaking.

  6. Response spectrum - Wikipedia

    en.wikipedia.org/wiki/Response_spectrum

    A series of mixed vertical oscillators A plot of the peak acceleration for the mixed vertical oscillators. A response spectrum is a plot of the peak or steady-state response (displacement, velocity or acceleration) of a series of oscillators of varying natural frequency, that are forced into motion by the same base vibration or shock.

  7. Modified Mercalli intensity scale - Wikipedia

    en.wikipedia.org/wiki/Modified_Mercalli...

    The basis by which the United States Geological Survey (and other agencies) assigns intensities is nominally Wood and Neumann's MM31. However, this is generally interpreted with the modifications summarized by Stover and Coffman because in the decades since 1931, "some criteria are more reliable than others as indicators of the level of ground ...

  8. Spectral acceleration - Wikipedia

    en.wikipedia.org/wiki/Spectral_acceleration

    Ground motion hazard map for Hawaii, based on a 2% probability of exceeding 0.2 second spectral acceleration at 5 Hz in 50 years. Spectral acceleration (SA) is a unit measured in g (the acceleration due to Earth's gravity, equivalent to g-force) that describes the maximum acceleration in an earthquake on an object – specifically a damped, harmonic oscillator moving in one physical dimension.

  9. 1994 Northridge earthquake - Wikipedia

    en.wikipedia.org/wiki/1994_Northridge_earthquake

    USGS seismologist Rufus Catchings suggested the intense shaking was localised and most of the city was unharmed. [19] A possible contributing factor for the effect is the local soil condition and topography. The maximum vertical pga recorded at the same station was 1.18 g. [18] Several sites in the valley also recorded pga exceeding 1.0 g. [20]