Geomorphological modelling and mapping of the Peru-Chile Trench by GMT

Abstract The author presents a geospatial analysis of the Peru-Chile Trench located in the South Pacific Ocean by the Generic Mapping Tool (GMT) scripting toolset used to process and model data sets. The study goal is to perform geomorphological modelling by the comparison of two segments of the trench located in northern (Peruvian) and southern (Chilean) parts. The aim of the study is to perform automatic digitizing profiles using GMT and several scripting modules. Orthogonal cross-section profiles transecting the trench in a perpendicular direction were automatically digitized, and the profiles visualized and compared. The profiles show variations in the geomorphology of the trench in the northern and southern segments. To visualize geological and geophysical settings, a set of the thematic maps was visualized by GMT modules: free-air gravity anomaly, geoid, geology and bathymetry. The results of the descriptive statistical analysis of the bathymetry in both segments show that the most frequent depths for the Peruvian segment of the Peru-Chile Trench range from -4,000 to -4,200 (827 recorded samples) versus the range of -4,500 to -4,700 m for the Peruvian segment (1,410 samples). The Peruvian segment of the trench is deeper and its geomorphology steeper with abrupt slopes compared to the Chilean segment. A comparison of the data distribution for both segments gives the following results. The Peruvian segment has the majority of data (23%) reaching 1,410 (-4,500 m to -4,700 m). This peak shows a steep pattern in data distribution, while other data in the neighbouring diapason are significantly lower: 559 (-4,700 m to -5,000 m) and 807 (-4,200 m to -4,400 m). The Chilean segment has more unified data distribution for depths of -6,000 m to -7,000 m. This paper presents GMT workflow for the cartographic automatic modelling and mapping deep-sea trench geomorphology.