Precursors Prior to the Parkfield, CA Earthquake

This figure shows the location of the Parkfield, CA earthquake and the location of the seismic array at Lajitas, TX. Note that the TXAR array is 1079 miles from the Parkfield epicenter and 1063 miles from the Gulf of Mexico epicenter.

Lajitas (TXAR) Array and Parkfield Earthquake locations

The results of the SeismicRadar processing are summarized below. The actual data produced by SeismicRadar is shown in the figures following. SeismicRadar has identified two precursors prior to the 28 September 2004 Parkfield earthquake. These two precursors were identified from seismic data located 1079 miles from the epicenter.


Event Arrival SNR Azimuth Horizontal Phase Velocity
P-wave 17:19:07 2040 292.38° 9.18 km/sec
"Precursor 1" 04:27:29 104 287.10° 9.19 km/sec
"Precursor 2" 17:06:50 99 294.77° 8.73 km/sec

SeismicRadar display of P-wave data captured by TXAR array. Associated raw waveform data.

SeismicRadar display of P-wave data captured by Lajitas (TXAR) array and associated raw waveform data.
Arrival Time: 17:19:07; SNR: 2040; Azimuth: 292.38°Velocity: 9.18 km/sec

SeismicRadar display of Precursor 1 data captured by TXAR array. Associated raw waveform data.

SeismicRadar display of "Precursor 1" data captured by Lajitas (TXAR) array and associated raw waveform data.
Arrival Time: 04:27:29; SNR: 104; Azimuth: 287.10°Velocity: 9.19 km/sec

SeismicRadar display of Precursor 2 data captured by TXAR array. Associated raw waveform data.

SeismicRadar display of "Precursor 2" data captured by Lajitas (TXAR) array and associated raw waveform data.
Arrival Time: 17:06:50; SNR: 99; Azimuth: 294.77°Velocity: 8.73 km/sec