Sea Level Budgets Should Account for Ocean Bottom Deformation.

The conventional sea level budget (SLB) equates changes in sea surface height with the sum of ocean mass and steric change, where solid-Earth movements are included as corrections but limited to the impact of glacial isostatic adjustment. However, changes in ocean mass load also deform the ocean bottom elastically. Until the early 2000s, ocean mass change was relatively small, translating into negligible elastic ocean bottom deformation (OBD), hence neglected in the SLB equation. However, recently ocean mass has increased rapidly; hence, OBD is no longer negligible and likely of similar magnitude to the deep steric sea level contribution. Here, we use a mass-volume framework, which allows the ocean bottom to respond to mass load, to derive a SLB equation that includes OBD. We discuss the theoretical appearance of OBD in the SLB equation and its implications for the global SLB.

The November 2017 Mw 5.5 Pohang earthquake: A possible case of induced seismicity in South Korea.

The moment magnitude (Mw) 5.5 earthquake that struck South Korea in November 2017 was one of the largest and most damaging events in that country over the past century. Its proximity to an enhanced geothermal system site, where high-pressure hydraulic injection had been performed during the previous 2 years, raises the possibility that this earthquake was anthropogenic. We have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks, constrain the geometry of this seismic sequence, and shed light on its causal factors. According to our analysis, it seems plausible that the occurrence of this earthquake was influenced by the aforementioned industrial activities. Finally, we found that the earthquake transferred static stress to larger nearby faults, potentially increasing the seismic hazard in the area.

Strong ground motion in normal - faulting earthquakes : Observations and their implications for earthquake hazard assessmentt and earthquake source processes

Normal-faulting earthquakes occur in regions of active extension, which include parts of western North American, the Aegean Sea region in the eastern Mediterranean, Italy, China, and New Zealand. The relative sparseness of ground acceleration data for normal faulting earthquakes and the widespread observation that active normal fault are segmented, such that a large earthquake may involved rupture of several fault segments in succession rather than a simgle fault, both cause difficulties in the quantification of ground acceleration in normal-faulting earthquakes. Some previous studies have suggested that a normal-faulting earthquake of a given size my be expected to produced much smaller ground acceleration than an earthquake of equivalent size with another focal mechanism type. This has led to suggestions that structures in regions where normal-faulting earthquakes of a given size are expected need not be designed to such stringent standards as those whereearthquakes of equivalent size but with ather focal mechanism types are expected (AU)