04/05/2018, M5.3 near Santa Cruz Is

  • 05 Apr 2018 12:29:16 PDT, (33.837, -119.725), depth 9.9km, 29km SW of Santa Cruz Is.
  • Foreshocks:No earthquakes were detected within 20 km of this earthquake in the preceding week. This is not unusual and is a reminder that earthquakes often occur without any previous short-term seismic activity.
  • Aftershocks: so far there have been no aftershocks recorded. Some may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • The earthquake occurred on an offshore strike-slip fault; further analysis will be needed to identify the fault or fault system with which it is associated. An earthquake of this size is not necessarily associated with a major, named fault. Nearby faults: Santa Cruz Island fault (14.2 km). The strike slip mechanism is shown below.
    Moment tensor solution for the 05 Apr 2018 earthquake near Santa Cruz Is.

  • Historic seismicity: two earthquakes with magnitudes of 4-5 have occurred in the general region since 1940 (M4.8 in 1954/08/26 and M4.1 2005/07/24). On December 21, 1812, a large earthquake struck in the Santa Barbara Channel, generating a tsunami that carried a ship inland. This earthquake is poorly understood due to its timing, but illustrates that offshore faults are capable of hosting earthquakes with magnitudes upwards of 7. On June 29, 1925, a magnitude 6.6 earthquake occurred offshore of Santa Barbara.
  • The earthquake was widely felt along the California coast as shown in the felt report plot below. Anything more than light shaking would only be expected on the channel islands, close to the epicenter.

    Instrumental shaking is shown in the ShakeMap below.

  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.

Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest station to the epicenter represented below is CI.LCP in Santa Maria, at a distance of 112 km from the event. The furthest station shown is CI.MLAC in Mammoth Lakes, over 400 km away. With an event of this magnitude, and the sensitivity of our seismic instruments, we detect this earthquake across our entire seismic network.

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