Identifying Active Faults in Northeast North America Using Hypocenters and Multiscale Edge Wavelet Analyses of Potential Fields

Abstract:

Multiscale edge Poisson wavelet analyses of potential field data ("worms") have a physical interpretation as the locations of lateral boundaries in a source distribution that exactly generates the observed field. The worm technique is therefore well-suited to analyses of crustal-scale stuctures that could be reactivated by tectonic stress or by fluid injection processes, providing new tools to analyze existing continental-scale data sets. Northeastern North America (US, Canada) hosts potentially damaging intraplate earthquakes, yet many of the Proterozoic structures are covered by thick sedimentary sequences or dense vegetation, and crustal structure is relatively poorly known.

For the purpose of extending basement structure beneath the Appalachian basin and establishing a consistent regional basis for comparison, we use worms to identify steeply dipping structures in compiled gravity and magnetic anomaly data sets. We compare results to intraplate earthquake locations to assess seismic hazards. Clearly, not all locations of lateral boundaries are faults, and we do not expect all faults to have shown activity in the ~50 years of seismic records available. However, proximity statistics between hypocenters and worms are of interest since they assist in the identification and location of a subset of potentially active faults. We compare structures of lateral mass-density or magnetization contrast with locations of earthquake hypocenters cataloged from the ISC, the NEIC, and the ANF from the EarthScope Transportable Array.

We develop a GIS based method for calculating hypocenter/worm proximity, and we will show statistics and maps from this method for the region at the meeting.