{'fraction_non_alphanumeric': 0.024793388429752067, 'fraction_numerical': 0.008640120210368144, 'mean_word_length': 5.1077981651376145, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Anatomy of an escape tectonic zone: Western Irian Jaya (Indonesia)

The western fold‐and‐thrust belt of New Guinea in Irian Jaya is presently a complex boundary, dominated by the Bird's Head block escape from the collision between the Australian plate and the remnants of volcanic belts carried by the Pacific plate. The escape rate given by geodetic measurements is of the order of 7 cm/yr, and movement is accommodated by a broad shear zone. We analyze this shear pattern using fault slip analyses performed in the field from 1992 to 1996, combined with focal mechanism inversions, moment tensors summations, and surface trace of structures inferred from radar and multispectral satellite images. Time control of the deformation is attained by isotope dating of the recent syntectonic intrusives. The geometry of the macro and microstructures occurred in two stages from the early Pliocene to the Present. The first stage (5 to 2 Ma) is marked by flat‐and‐ramps structures guided by N60°E lateral ramps associated with a N60°E cleavage, affecting the whole of western Irian Jaya. The second stage (2 Ma to Present) shows the collapse of the western fold‐and‐thrust belt and the escape of the Bird's Head and the Lengguru belts along N60°E transtensile faults. In the latter stage, the strike‐slip offset is distributed on the N60°E schistosity zone along which some fracture planes are reactivated as left‐lateral transtensile faults. Shallow earthquakes moment tensors have been inverted for stress and summed to get strain rates to define contrasting structural provinces. The spatial variations in both stress and strain fields from earthquakes and microtectonics show that (1) they are consistent and are assumed to be coeval, (2) they reveal that oblique convergence is partitioned, and (3) they are influenced by the existence of a free boundary. We see no significant rotation of stress axes laterally along the escape zone. Instead, stresses change according to the different orientations of basement structures and thus undergo rapid spatial variations or principal axes permutations. Eastward, in front of the Australian craton, the oblique convergence is partly distributed on reverse and strike‐slip faults. Westward, along the NW part of the craton, we infer the Seram trench is a free boundary which allows material to escape. These results show that the evolution of the escape zone depends on the importance of the geometry of the former margin of Australia (e.g., tilted blocks), which controls the style deformation relative to the regional stress, and the boundary conditions, which control the variation of the state of stress through time.