A MATLAB GUI for Examining Triggered Tremor: A Case Study in New Zealand

Abstract

We introduce a user‐friendly MATLAB GUI (graphical user interface) software for searching for triggered tectonic tremor. This software includes the following features: (1) multiple panels, whose primary function screen shows seismograms filtered at various frequency bands, surface‐wave seismograms or spectrograms for comparison, and a station map; (2) a tag function with which users can classify each station by quality and/or group and whose results will show on the map; (3) the locations of tremor sources from which users can manually pick the arrival times of individual tremor bursts and quickly obtain preliminary locations; and (4) output visualization from which users can align triggered tremor as a move‐out plot or save snapshots to a PDF file. For demonstration, we apply this package to examine triggered tremor in New Zealand between 2004 and 2016. We analyze 5300 seismograms from 18 M_w ≥ 7.5 target earthquakes and find that 9 generate triggered tremors in six regions in the central and the northern Hikurangi subduction margin, the central strike‐slip Alpine fault, Kaikōura and Southland in the South Island, and Northland in the North Island. The minimum apparent tremor‐triggering stress observed at the surface stations in these regions varies from 5.0 to 16.6 kPa. This GUI‐based package can facilitate the process of analysis for identifying triggered seismic events from a sizeable seismic dataset.