There was a series of earthquakes in this area a few years ago, which came to my mind. However, this M 7.1 was much deeper. <\/p>\n
This M 7.1 earthquake was quite deep (over 500 km!). Those earlier events were shallower and appear to have been related to the Flores thrust fault. Read more about these shallower earthquakes here<\/a>.<\/p>\n This part of the world is geologically dominated by the convergent plate margin between the Australia and Eurasia plates. This convergent plate margin is part of the Alpide belt, a convergent plate margin that spans almost half the globe (from the northern tip of Australia to the western tip of Portugal). The Alpide belt is responsible for building the tallest mountains in the world (the Asian Himalayas and the European Alps). <\/p>\n Here, in Indonesia, the Australia plate dives beneath the Australia plate forming a subduction zone and a deep sea trench (the Java trench). Earthquakes along this megathrust subduction zone fault have generated strong ground shaking, generated tsunami, and triggered landslides in the past.<\/p>\n In this part of the world, the Eurasia plate is subdivided into a sub-plate called the Sunda plate (so one might see maps with either name labeling this plate). <\/p>\n As the Australia plate subducts it starts out dipping shallowly beneath Java, Bali, Lombok, and the other islands. <\/p>\n The oceanic crust has water within it that helps generate melt in the magma that exists above the Australia plate and beneath the Sunda plate. When this magma melts, its density decreases and the magma rises until it erupts forming the volcanoes that comprise these islands.<\/p>\n As the Australia plate subducts further, the angle that it dips down into the Earth gets steeper. During this process the plate bends and gets exposed to higher pressures (and temperatures). <\/p>\n These physical processes change the stresses within and surrounding the plate. These changes in stress can cause earthquakes like the M 7.1.<\/p>\n Even though this earthquake was large in magnitude, it was so deep so that the shaking intensity was smaller. <\/p>\n The shaking intensity is often reported using the Modified Mercalli Intensity (MMI) scale. People (anyone with internet access) can report their observations on the USGS “Did You Feel It?” web page for this earthquake. <\/p>\n These observations are then used to estimate the shaking intensity felt by those people. Reports from this earthquake show that people on these nearby islands felt intensities around MMI 4 to MMI 5 or so.<\/p>\n It's been a busy few days for earthquakes! We just released a post about yesterday's M7.1 ultra-deep quake in the Bali Sea. Yesterday we wrote about a M3.6 in Ohio, and the day before that a M5.7 in western Colombia. Subscribe to our newsletter – you'll become great at geography! pic.twitter.com\/SE2FhLi4CJ<\/a><\/p>\n — Dr. Judith Hubbard (@JudithGeology) August 29, 2023<\/a><\/p><\/blockquote>\n Below is my interpretive poster for this earthquake<\/font><\/H2><\/p>\n
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I include some inset figures. Some of the same figures are located in different places on the larger scale map below. In some of these inset figures I place a blue star to locate the M 7.1 earthquake on these figures.<\/font><\/H3><\/p>\n
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20230828_indonesia\/20230828_indonesia_interpretation.jpg\")
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20230828_indonesia\/cross_section_java_margin_20230828.jpg\")
<\/a><\/p>\n<\/ul>\nOther Report Pages<\/font><\/strong><\/H2><\/p>\n
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