A magnitude 7.8 earthquake struck New Zealand’s South Island at 12:02 a.m. Monday. The seismometer housed in GRCC’s geology lab recorded the earthquake approximately 19 minutes later. The first waves seen in the seismograms below are called body waves, they travel through the Earth, and are the fastest seismic waves. The later waves, that look more spread out, are surface waves. They travel along the surface of the Earth and are responsible for most of the damage caused by earthquake shaking. The earthquake was generated by movement along a fault close to the juncture of two tectonic plates. The nature of movement led to activation of the tsunami warning system in coastal communities close to the main shock. Evacuating residents were further rattled by dozens of aftershocks over the next 9 hours, some as large as magnitude 6.5. For more information about this and other earthquakes visit the United States Geologic Survey’s website.