Quake clamps down on slow slip

Abstract

Using continuous GPS (cGPS) data from the Hikurangi subduction zone in New Zealand, we show for the first time that stress changes induced by a local earthquake can arrest an ongoing slow slip event (SSE). The cGPS data show that the slip rate in the northern portion of the 2013/2014 Kapiti SSE decreased abruptly following a nearby intraslab earthquake. We suggest that deceleration of the Kapiti SSE in early 2014 occurred due to a tenfold increase in the normal stress relative to shear stress in the SSE source, induced by the nearby M w 6.3 earthquake, consistent with expectations of rate and state friction. Our observation of an abrupt halting/slowing of the SSE in response to stress changes imposed by a local earthquake has implications for the strength of fault zones hosting SSEs and supports the premise that static stress changes are an important ingredient in triggering (or delaying) fault slip.

Slow slip events and the 2016 Te AraroaMw7.1 earthquake interaction: Northern Hikurangi subduction, New Zealand

“…These observations were supported also by numerical simulations suggesting that SSEs have the potential to trigger earthquakes [Segall and Bradley, 2012]. Wallace et al [2014] showed that the change in stress induced by the 2013 M w 6.3 Eketahuna earthquake arrested an ongoing nearby SSE, while in other cases earthquakes have triggered nearby SSEs [François-Holden et al, 2008]. Wallace et al [2014] showed that the change in stress induced by the 2013 M w 6.3 Eketahuna earthquake arrested an ongoing nearby SSE, while in other cases earthquakes have triggered nearby SSEs [François-Holden et al, 2008].…”

Triggered Slow Slip and Afterslip on the Southern Hikurangi Subduction Zone Following the Kaikōura Earthquake

“…The cumulative moment released thus far beneath the northern South Island is equivalent to a M W 7.4 earthquake. The distribution and duration of the triggered Kapiti SSE is similar to past Kapiti SSEs (Wallace et al, 2014;Wallace & Beavan, 2010). To test whether or not afterslip on the subduction zone is required by the data, we have undertaken inversions of the GPS and InSAR data assuming slip on crustal faults only (no subduction interface slip beneath Marlborough) and obtain a substantially worse fit to the data (reduced chi-square, χ 2 n = 1.16 for our model with the interface versus χ 2 n = 1.88 for the model with only crustal faults).…”

“…SSEs have been observed at the southern Hikurangi margin, in the Kapiti and Manawatu regions, at 25-40 km depth, encircling a region of deep interseismic coupling at the southern Hikurangi margin Beavan, 2006, 2010;Figure 1a). Past Kapiti SSEs occurred in 2003, 2008, and 2013, while previous Manawatu SSEs were during 2004/2005/2011, and 2014(Hamling & Wallace, 2015Wallace & Beavan, 2010;Wallace et al, 2014). Past Kapiti SSEs occurred in 2003, 2008, and 2013, while previous Manawatu SSEs were during 2004/2005/2011, and 2014(Hamling & Wallace, 2015Wallace & Beavan, 2010;Wallace et al, 2014).…”

Tectonic tremor along the northern Hikurangi Margin, New Zealand, between 2010 and 2015

“…These events last for 1–3 weeks and release energy equivalent to M w 6.3–6.8 [ Beavan et al ., ; Wallace and Beavan , ]. Conversely, SSEs in the south primarily occur every 5 years at depths between 35 and 60 km and last for 12–18 months; these SSEs release energy equivalent to ~ M w 7.0 [ Wallace et al ., , ]. These larger SSEs in the south accommodate a large fraction of the plate motion and perturb the stress field to the extent that they may trigger shallow SSEs in the north [ Wallace et al ., ].…”