This place has had some recent seismicity (largest magnitude M 6.5; Kato, 2023), though I did not write up a report. <\/p>\n
This earthquake was a shallow crustal fault earthquake associated with the Noroshi-oki fault<\/a>. <\/p>\n This fault is a crustal reverse fault (compressional) that dips to the southeast. Kato (2023) plotted seismicity from a previous sequence and I include the plots from their paper below. These plots reveal the orientation of this fault system.<\/p>\n The aftershock pattern (see poster below) suggests that the entire fault slipped during (or shortly before or after) this M 7.5 mainshock.<\/p>\n There was a tsunami generated by this earthquake. Below are plots from the gages that have a clear record of the tsunami.<\/p>\n The nearest gage (Noto) is located very close to the epicenter and the data suggest that the gage has been damaged in some way.<\/p>\n Empirical fault scaling relations are ways that we can compare fault rupture sizes with earthquake magnitudes. One of the most used and well cited empirical fault scaling relations paper is Wells and Coppersmith, 1994.<\/p>\n Here is the USGS fault slip model for the M 7.5 earthquake. The length of the fault slip figure is about 40 kilometers (km) and the width of the fault is about 45 km. The color represents the amount that the fault slipped (in meters) during the earthquake. So, the slip area does not fill this entire area. Most of the slip length is within ~180 km and width is within ~180km. The maximum slip is ~3.7 meters.<\/p>\n If we look at the spatial extent of aftershocks (which may indicate the slip region of the earthquake), the length is about 150 km. This is slightly shorter than the USGS fault slip model.<\/p>\n Here is a plot from Wells and Coppersmith that shows the data relating magnitude with subsurface rupture length. We can see that there is a positive relation between magnitude and length (as the length is larger, so is the magnitude).<\/p>\n \n(a) Regression of subsurface rupture length on magnitude (M). Regression line shown for all-slip-type relationship. Short dashed line indicates 95% confidence interval. (b) Regression lines for strike-slip relationships. See So, I used these scaling relations to calculate the magnitude for earthquakes of varying subsurface fault length. Here is a table from those calculations.<\/p>\n \nTectonic settings of the study region (black box). The solid sawtooth lines and the black dashed line denote the plate boundaries (Bird 2003). The red triangles denote the active volcanoes. The blue dashed lines and the pink lines denote the depth contours to the upper boundary of the subducting Pacific slab and that of the subducting Philippine Sea slab, respectively (Hasegawa et al. 2009; Zhao et al. 2012). The topography data are derived from the GEBCO_08 Grid, version 20100927, http:\/\/www.gebco.net. The ages of oceanic plates are from M\u00a8uller et al. (2008).\n<\/p><\/blockquote>\n<\/ul>\n\n
\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20240101_japan\/WSL_tide_gage_plot_toyama_20240101.jpg\")
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20240101_japan\/WSL_tide_gage_plot_sado_20240101.jpg\")
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20240101_japan\/WSL_tide_gage_plot_saigo_20240101.jpg\")
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20240101_japan\/WSL_tide_gage_plot_fukaura_20240101.jpg\")
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20240101_japan\/WSL_tide_gage_plot_hamada_20240101.jpg\")
<\/a><\/p>\n<\/ul>\nFault Scaling Relations<\/font><\/H3><\/p>\n
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20240101_japan\/20240101_japan_75_slip.png\")
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20230908_morocco\/wells_coppersmith_1994_fig_14.jpg\")
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\nTable 2 for regression coefficients. Length of regression lines shows the range of data for each relation.\n<\/p><\/blockquote>\n
\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20240101_japan\/wells_coppersmith_20240101_M7p5_japan.jpg\")
<\/a><\/p>\nBelow 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.<\/font><\/H3><\/p>\n
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20240101_japan\/20240101_japan_interpretation.jpg\")
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\n![\"\"](\"https:\/\/earthjay.com\/earthquakes\/20240101_japan\/20240102_japan_tide_gage_interpretation.jpg\")
<\/a><\/p>\n<\/ul>\nOther Report Pages<\/font><\/strong><\/H2><\/p>\n
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Some Relevant Discussion and Figures<\/font><\/strong><\/H2><\/p>\n
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\n![\"\"](\"http:\/\/earthjay.com\/earthquakes\/20141122_honshu\/Level3_SF_Final-06_fig_2.jpg\")
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\n![\"\"](\"http:\/\/earthjay.com\/earthquakes\/20141122_honshu\/Level3_SF_Final_fig85.jpg\")
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\n![\"\"](\"http:\/\/earthjay.com\/earthquakes\/20180905_japan\/liu_etal_2013_seismic_anisotropy_southern_kuril_arc_fig_01.JPG\")
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