First Version of Japan Unified High-resolution Relocated Catalog for Earthquakes by JUICE Project

Abstract:

The objective of Japan Unified High-resolution Relocated Catalog for Earthquakes (JUICE project) is to understand the tectonic processes, seismogenic zones, and active fault evaluations. We have completed the first version of catalog by JUICE project for the Japan Islands where the shallow (> 40 km) earthquakes up to M6.9 between years of 2001 and 2013. Events were relocated using the Double-Difference method for high-resolution earthquake location. NIED High-Sensitivity seismic observation (Hi-net) has been established in 2000 to observe micro-earthquakes in Japan. We take advantage of having such good and big data to revisit the problem in the past using these Hi-net data.

We collect NIED Hi-net hypocenter catalog, Hi-net P and S arrival data, and waveforms of magnitude up to M6.5 and down to depth of 40 km from year of 2001/Jan to 2013/Dec. Then we apply our data set to the double-difference algorithm (hypoDD) by Waldhauser and Ellsworth (2000) for high-resolution hypocenter locations.

It turns out to be that we relocate over 1,000,000 events for JUICE project and these events are now confined into appropriate clusters and lines. An example of applying this catalog by JUICE project is to estimate the cutoff depth where 90 % of earthquake occurred (D90) (Omuralieva et al., 2012). We now estimate the cutoff depth where 95 % of earthquake occurred (D95) by using the JUICE catalog. D95 is mainly around 15 km under the Japan Island while there the strong spatial variation throughout the Japan Island. However, some of these variations may be due to hypocenters being contaminated by intra and inner slab events and misleading a seismogenic zone for fault related events to be deeper. Since the new high-resolution catalog makes easier to distinguish hypocenters into different types, it gives shed to more detail studies. In our presentation, we will show the new JUICE catalog and its applications.