‘Wobble’ may precede some great earthquakes

Science Daily  April 29, 2020 The land masses of Japan shifted from east to west to east again in the months before the strongest earthquake in the country’s recorded history, a 2011 magnitude-9 earthquake. An international team of researchers (Germany, Chile, USA- Ohio State University) analyzed the “wobble,” may have the potential to alert seismologists to greater risk of future large subduction-zone earthquakes. The imperceptible movement was obvious in data recorded by more than 1,000 GPS stations distributed throughout Japan, in the months leading up to the March 11 Tohoku-oki earthquake. They saw a reversing shift in the land — […]

Injection wells can induce earthquakes miles away from the well

Science Daily  August 30, 2018 Researchers at UC Santa Cruz analyzed spatial seismicity decay in a global dataset of 18 induced cases with clear association between isolated wells and earthquakes. They found two populations. The first is characterized by near-well seismicity density plateaus and abrupt decay, dominated by square-root space-time migration and pressure diffusion. Injection at these sites occurs within the crystalline basement. The second population exhibits larger spatial footprints and magnitudes, steady spatial decay over more than 10 kilometers, potentially caused by poroelastic effects. Far-reaching spatial effects during injection may increase event magnitudes and seismic hazard beyond expectations based […]