# What is the lateral ground acceleration, at the fault line, during a strike-slip earthquake?

I've read that peak lateral ground acceleration for magnitude 7 - 8 earthquakes is ~1 g at the epicenter (is that correct?), but I'm wondering if it might be significantly higher right at the rupturing fault itself. This paper compares theoretical models of this motion but, in scanning through it, I didn't find any empirical measurements:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011JB009097?fbclid=IwAR0yy3vmLouk8jNz8FlIqPddj-HA4Npyh6rHQSS_qZ12aR29aM2jkkqK1EU

What is the approximate range of lateral ground acceleration (and peak velocity), as a function of earthquake magnitude, right at the fault, for strike-slip earthquakes?

## 1 Answer

It can be high but is bounded because the slip velocity on fault (as it slips during an earthquake) is usually of the order of 1-3 m/sec.

Kaikoura earthquake (M7.8 strike slip event) had a max PGA of 3.1 g (second highest ever recorded) but it is attributed due to flapping effect. See here for more details.

• Thanks for the reference. Yes, as you mention, the 3.1 g is an artifact caused by local rebounding: "Our results suggest that the extremely large accelerations recorded at seismic station WTMC do not reflect the actual ground shaking, but were caused by a local, system response around the sensor." Oct 13 '19 at 6:04