Warnings regarding the potential threat from tectonic plate movements\nhave been repeatedly issued by the government, specifically the\nMeteorology, Climatology, and Geophysics Agency (BMKG), as well as\ndisaster experts. The intention of these warnings is not to cause panic,\nbut to serve as a reference for disaster mitigation to reduce fatalities\nand aim for zero victims.<\/p>\n
While much attention is focused on the potential for massive\nmegathrust earthquakes accompanied by tsunamis\u2014with Indonesia surrounded\nby 14 megathrust segments\u2014there is another potential source of disaster\nthreatening the island of Java. Daryono from the Indonesian Disaster\nExpert Association (IABI) stated that it is vital to be alert to the\npotential for large earthquakes in Java, which requires a deep\nunderstanding of tectonic mechanisms, particularly the threat\noriginating from the subduction zone of the Indo-Aussie Plate diving\nbeneath the Eurasian Plate.<\/p>\n
\u201cFor a long time, public attention has been focused on the potential\nfor megathrust earthquakes located at shallow plate contact zones that\nrisk triggering large tsunamis. However, there is another threat that is\nno less destructive: intra-slab earthquakes (within the plate),\u201d he said\non Saturday (5\/9\/2026).<\/p>\n
\u201cIntra-slab earthquakes occur due to the process of deformation and\nfaulting occurring within the subducted plate at intermediate depths\n(60-300 km) to deep levels (above 300 km),\u201d he added.<\/p>\n
According to Daryono, intra-slab earthquakes occur due to the\nbreaking, cracking, or faulting of rocks within the oceanic plate that\nis diving beneath the continental plate. This is triggered by three main\nfactors: gravitational pull (slab pull) that cracks the plate body like\na heavily loaded biscuit; intense bending pressure that causes the plate\nstructure to snap like an extremely bent plastic ruler; and rock\ndehydration, where geothermal heat \u2018squeezes\u2019 water out of minerals,\ncreating internal pressure that makes the plate brittle and prone to\nfracturing.<\/p>\n
\u201cThe mechanical characteristics of intra-slab earthquakes often\ntrigger high-magnitude ground motion and wave frequencies that produce a\nvery wide shaking spectrum,\u201d he said.<\/p>\n
Historical seismicity records in Java prove the massive seismic\nimpact of intra-slab events. Events such as the 1867 Java Earthquake\n(M7.8), the 1903 West Java\/Banten Earthquake (M7.9), and the 1943\nCentral Java Earthquake (M7.1) serve as empirical evidence that the\nrelease of tectonic stress energy within the plate slab can shake\nmultiple provinces and claim many lives.<\/p>\n
History records several intra-slab earthquake events in Java,\nincluding:<\/p>\n
10 June 1867, M7.8: 500 deaths and widespread damage across\nalmost the entire island of Java.<\/p><\/li>\n
28 March 1875, M7.6: Widespread damage across almost all of\nJava.<\/p><\/li>\n
27 February 1903, M7.9: Highly destructive in Banten, West Java,\nand Lampung.<\/p><\/li>\n
23 July 1943, M7.1: Damage occurred in Cilacap, Tegal,\nPurwokerto, Kebumen, Purworejo, Bantul, and Pacitan, with over 213\ndeaths.<\/p><\/li>\n
2 September 2009, M7.0: 108 deaths.<\/p><\/li>\n
10 April 2021, M7.0: 10 deaths, with damage across 16 regencies\nand cities.<\/p><\/li>\n<\/ol>\n
\u201cEven medium-scale events, such as the Cilacap M5.3 earthquake on 4\nSeptember 202_6, which was triggered by a normal fault due to slab pull\nand plate bending and felt as far as East Java, are types of intra-slab\nearthquakes,\u201d he noted.<\/p>\n
\u201cThis phenomenon confirms that if an intra-slab earthquake reaches a\nmagnitude of M6.0 or higher, S-waves (shear waves) propagating\nefficiently through the dense rock structure of the plate slab will\nmultiply the level of infrastructure damage on the surface,\u201d Daryono\nexplained.<\/p>\n
Regarding anticipation, Daryono stated that the primary step in\nmitigating intra-slab earthquakes lies in the integration of\nstrengthened seismological analysis and structural mitigation\nengineering.<\/p>\n
\u201cFrom a seismological perspective, mapping stress field zones and\nreal-time microseismic monitoring of the subducted lithosphere is\ncrucial to identify areas of rock acceleration that are prone to\ncollapse,\u201d he said. \u201cThis seismic information must serve as the primary\nbasis for updating the seismic hazard maps for the Java region. At the\nsite level, the implementation of earthquake-resistant building codes\nbased on Peak Ground Acceleration (PGA) is the most absolute line of\ndefence,\u201d he emphasised.<\/p>\n
While intra-slab earthquakes do not trigger tsunamis, Daryono warned\nthey should not be ignored. \u201cGiven that intra-slab earthquakes do not\ntrigger tsunamis but dominate high-frequency ground shaking, the\nresilience of earthquake-resistant physical construction and spatial\nplanning readiness is key. Therefore, remain alert to the potential of\nintra-slab earthquakes,\u201d Daryono concluded.<\/p>", "url": "https:\/\/jawawa.id\/newsitem\/beyond-megathrust-experts-warn-of-intra-slab-earthquake-threats-to-java-1788601980", "image": "" }, "sponsor": "Okusi Associates", "sponsor_url": "https:\/\/okusiassociates.com" }