Correlations between earthquake recurrence and paleolake changes in Surprise Valley, CA

Brian Marion
May 2015

Introduction and Purpose

Evaluating seismic hazard and fault activity in a region with a low strain rate is challenging, largely because the earthquake recurrence interval exceeds historical seismicity records. The northwestern Basin and Range (NWBR) (Figs. 1 & 2) is one such region. Surprise Valley in the NWBR (Fig. 3) is bound by the Surprise Valley fault (SVF), an active normal fault with at least five earthquakes of M 6.8-7.3 since 35 ka and an irregular recurrence interval (Personius et al., 2009). Surprise Valley also hosted a pluvial lake (Fig. 2) that reached its highstand ~15 ka (Ibarra et al., 2014); additional dated paleoshorelines constrain the lake level history over the last 25 ky. These two datasets, in combination with high resolution topography, allow us to ask the following questions:

  • How are earthquakes and slip distributed along the SVF?
  • How do earthquakes and slip change over time?
  • What role, if any, has pluvial Lake Surprise played on the spatial and temporal variations of slip along the SVF?

Both the filling of reservoirs (Bell and Nur, 1978; Gupta, 2002) and removal of pluvial lakes (Oldow and Singleton, 2008; Weldon, 2009) have been shown to induce earthquakes. In the Summer Lake basin (Fig. 2), an earthquake cluster correlates with rapid removal of Lake Chewaucan (Weldon, 2009), and seismogenic landslides were facilitated by the heightened water table associated with the lake (Badger and Watters, 2004). It is this rapid change in water volume, both an increase and decrease that can alter the stress environment, through a combination of the change in stress state, change in pore fluid pressure in saturated rocks, raising of the water table, and lubrication of the faults, to induce seismicity. During Lake Surprise’s highstand, it had a volume of 218 km3, which equates to an increased load on the bedrock and underlying faults (Ibarra et al., 2014). The irregular earthquake recurrence interval determined by Personius et al. (2009) may be explained with the equally variable changes in lake level for Lake Surprise during the Pleistocene. Overlaying the information provided in Personius et al. (2009) with Ibarra et al. (2014)’s lake level history suggests a potential correlation: a cluster of earthquakes occurs at the same time as a rapid decrease in lake level (Figs. 4 & 5)

Additional research is needed to substantiate and quantify this initial correlation. In order to further explore this correlation and address my research questions, I will

  1. Document offset of paleoshorelines across the SVF through lidar-based mapping;
  2. Correlate lake level history with earthquakes;
  3. Obtain radiocarbon dates on paleoshoreline tufas;
  4. Determine how offset and slip rate vary along strike of the SVF.

Full Thesis Proposal (PDF format)