Katrina Jacobs

Katrina Jacobs profile picture

Qualifications

B.S., University of South Dakota (2005), MS Geophysics, University of Alaska Fairbanks (2008), PhD Geophysics Victoria University of Welington (2013).

Publications

Boese , C., Jacobs , K., Smith , E., Stern , T., & Townend, J. (2014). Background and delayed- triggered swarms in the central Southern Alps,South Island, New Zealand. Geochemistry, Geophysics, Geosystems, 15(4), 945-964.

Jacobs, K., Smith, E.G.C., Savage, M.K., Zhuang, J. (2013). Cumulative rate analysis (CURATE): A clustering algorithm for swarm dominated catalogs. Journal of Geophysical Research - Solid Earth, 118(2), 553-569.

Jacobs, K.M., & McNutt, S.R. (2010). Using seismic b-values to interpret seismicity rates and physical processes during the preeruptive earthquake swarm at Augustine Volcano 2005–2006. In J.A. Power, M.L. Coombs, & J.T. Freymueller (Eds.), The 2006 eruption of Augustine Volcano, Alaska: U.S. (chapter 3, p. 59–83). Geological Survey Professional Paper 1769.

Research interests

My main area of research interest in is in using the occurrence of earthquakes to better understand the driving forces behind earthquake rates and the physical state of regions where they occur. My work to date has largely focused on earthquake swarms, which are sets of spatially clustered events occurring over a relatively short amount of time. Unlike mainshock-aftershock sequences swarms do not typically contain one dominant large magnitude earthquake, and the largest magnitude event is often not at the beginning of the sequence. Earthquake swarms occur commonly in volcanic and geothermal settings, but are also observed in classic tectonically driven environments. Swarms likely represent different physical processes than mainshock-aftershock sequences that we associate with tectonic loading. My Masters research at the University of Alaska Fairbanks focused on seismic b-values (ratio of small to large magnitude earthquakes) during earthquake swarms accompanying volcanic unrest and eruptions at various Alaskan volcanoes. That work showed that stress, when present, is the dominant physical property controlling seismic b-values. For my PhD I studied earthquake sequences in New Zealand with Euan Smith and Martha Savage.  We created an objective way to better identify swarm sequences in earthquake catalogs using earthquake rate as the main parameter for sequence selection. This method allowed us to investigate the magnitude and rate properties of swarms. We found several unique patterns of rate, and also showed that about 55% of swarm activity is governed by a similar temporal decay to aftershock sequences. The amount of swarms that behave as aftershocks has implications for future earthquake forecasts, which typically use aftershock laws and decay laws. Our method also revealed a few previously unidentified earthquake swarms that accompany slow slip event along the Hikurangi margin.

My interest in earthquake timing and volcanoes has led to an EQC funded postdoc project with Nico Fournier (GNS) and Martha Savage (VUW) in which we will investigate whether (and how) slow slip events on the Hikurangi margin influence the Taupo Volcanic Zone (TVZ). Volcanic and geothermal areas are more sensitive to local earthquake triggering from large far-field earthquakes than more purely tectonic regions. With this research we hope to address whether volcanic areas in New Zealand are similarly sensitive to large slow slip events. We will focus around Lake Taupo and the southern TVZ quantifying observed strain and strain rate at the time of large slow slip events using the existing continuous GeoNet GPS network. These observations will be compared to models of strain produced using an existing dynamic numerical model to quantify strain changes in the southern end of the TVZ during slow slip events. We will then use a number of seismological methods to characterize the state of the volcanic areas at the time of slow slip events and any other observed changes in strain. This investigation of strain will address a time scale (days to months) which has not been examined despite observations on both shorter and longer time scales. Slow slip events occur regularly along the Hikurangi subduction zone and this study will assess whether these events have a direct impact on the state of the TVZ and volcanic hazards.