Abstract
The earthquake environmental effects (EEEs) around the epicentral area of the Pohang earthquake (Mw-5.4) that occurred on 15 November 2017 have been collected and classified using the Environmental Seismic Intensity Scale (ESI-07 scale) proposed by the International Union for Quaternary Research (INQUA) focus group. The shallow-focus 15 November Pohang earthquake did not produce any surface rupture, but caused extensive secondary environmental effects and damage to life-line structures. This earthquake was one of the most damaging earthquakes during the instrumental seismic era of the Korean Peninsula. The EEEs included extensive liquefaction, ground cracks, ground settlement, localized rockfall, and variation of the water table. The main objective of this paper was to carry forward a comparative assessment of the Pohang earthquake’s intensity based on traditional macroseismic scales and the ESI-07 scale. With that objective, this study will also make a substantial contribution to any future revision of the ESI-07 scale, which mostly comprises case studies from Europe and South America. The comparison of the ESI-07 scale with traditional intensity scales similar to the intensity scale used by the Korean Meteorological Administration for the epicentral areas showed 1–2-degree differences in intensity. Moreover, the ESI scale provided a clearer picture of the intensity around the epicentral area, which is mostly agricultural land with a lack of urban units or buildings. This study urges the integration of the traditional and ESI-07 scale for such small magnitude earthquakes in the Korean Peninsula as well as around the world in future. This will predict seismic intensity more precisely and hence provide a more-effective seismic hazard estimation, particularly in areas of low seismic activity. The present study will also provide a useful and reliable tool for the seismic hazard assessment of similar earthquakes around the study area and land-use planning at a local scale considering the secondary effects.
Highlights
The 12-degree Environmental Seismic Intensity (ESI-07) scale was introduced by the InternationalUnion for Quaternary Research (INQUA) in 2007 and is mainly based on earthquake environmental effects (EEEs)
Several EEEs were induced by the Pohang earthquake around the epicentral area, which is known as the Heunghae Basin
This may be because the Modified Mercalli intensity scale (MM) intensity used here was taken from the USGS, which is estimated from the estimated peak ground acceleration (PGA) and PGV and is not calibrated according to the damage survey, whereas Korea Meteorological Administration (KMA) intensity is calibrated to the local geology and damage observed during the earthquake
Summary
The 12-degree Environmental Seismic Intensity (ESI-07) scale was introduced by the International. Use damage to human-built structures to assess intensity, which mainly reflects the cultural and economic development of the area instead of the strength of the earthquake, which is one of the major setbacks for the use of traditional intensity scales in seismic hazard assessment for an area [12,17,18] To overcome this problem in traditional intensity scales, several studies have compiled EEEs from diverse tectonic settings, geological settings, and earthquakes of diverse origin and proposed the ESI-07 intensity scale under the framework of INQUA [1,3,4,17,19,20,21]. The results obtained indicate that the ESI-07 scale intensity is higher than the traditional intensity scale, which will help in making a more precise seismic hazard estimation, in areas of low seismic activity
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