The mechanism of the tearing of the Java subducting plate comes from the constraints by surface bathymetry data and earthquake depth

Abstract

The tearing of the subducting plate, which also named slab window, is prominent in the Java subduction zone. Mantle tomography data indicate plate tearing, supported by short-lived activity of K-rich volcanoes. Despite the acknowledged tearing phenomenon, the formation mechanism is less understood. Along the trench (95°E-120°E), we conducted 1707 profiles at 10 km intervals perpendicular to the subduction zone. Using five key parameters (1. Depth of the input oceanic plate; 2. Oceanic age of the input plate; 3. Trench depth; 4. Accretionary prism crest; 5. Accretionary prism slope), we illustrated bathymetric changes along each profile. Furthermore, utilizing data from over 40,000 earthquake depths, we imaged the subduction plate's configuration. Our study reveals distinct characteristics in the Java subduction system (110°-115°E). The input plate is 2500-3000 m shallower, the trench depth is 800-1200 m shallower, the accretionary prism crest is 1500-2000 m shallower, and the subduction angle is approximately 15° lower than surrounding subducting zones. A correlation between slab dip angles and the depth of the trench and prism crest indicates that the anomalous shallower bathymetry in the 110-115°E region is likely due to the decreased slab dip angles. This suggests that, at present, there is less likely thick buoyant oceanic crust is subducted beneath the Java trench, blocking its subduction and forming a slab window evident in tomography data.