The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Search
Advanced search
OR
Browse
Search
Volume 123, Issue 1
Displaying 1-4 of 4 articles from this issue
Show all abstracts
    • |<
    • <
    • 1
    • >
    • >|
Articles
  • Surface rupture and slip associated with the 2014 Nagano-ken Hokubu earthquake（Mw6.2）
    Aya Katsube, Hisao Kondo, Kaoru Taniguchi, Yuko Kase
    2017 Volume 123 Issue 1 Pages 1-21
    Published: January 15, 2017
    Released on J-STAGE: April 18, 2017
    DOIhttps://doi.org/10.5575/geosoc.2016.0048
    JOURNAL FREE ACCESS
    Show abstractHide abstract

    On 22 November 2014, the Kamishiro Fault, situated along the northernmost segment of the Itoigawa-Shizuoka Tectonic Line, ruptured, causing the Mw 6.2 Nagano-ken Hokubu earthquake. We mapped a 9-km-long surface rupture along the Kamishiro Fault, monitored earthquake-related deformation, and measured co-seismic displacements at 42 localities. The surface rupture consists of main and additional sections. The maximum vertical displacement is 95±17 cm at Shiojima, and the amount of displacement generally decreases to the south. The main and additional rupture traces are divided by a 1-km-wide step-over. The slip distribution and fault geometry indicate that the earthquake rupture terminated at this structure, preventing it from propagating farther to the south. The length of the surface rupture is shorter than the total length (24 km) of the Kamishiro Fault. The main shock epicenter is located near the northern end of the surface rupture, and the aftershock distribution indicates that the source fault extends farther to the north. The relationship between the maximum net displacement of 2.0 m and the surface rupture, or source fault lengths, show a good fit with empirical data. Historical documents suggest that a similar-sized earthquake occurred in the same region in 1714 AD, indicating they may occur at an interval of ~300 years. The 2014 earthquake was a partial rupture on the Kamishiro Fault, unlike the characteristic earthquakes modeled in long-term predictions. A paleo-seismic reconstruction of displacement along the Kamishiro Fault is necessary to understand the recurrence intervals of both irregular and characteristic earthquakes.

    View full abstract
    Download PDF (9094K)
Report
  • Petrography and whole-rock major and trace element analyses of igneous rocks from Iheya North Knoll, middle Okinawa Trough, SIP Expedition CK14-04 (Exp. 907)
    Toru Yamasaki
    2017 Volume 123 Issue 1 Pages 23-29
    Published: January 15, 2017
    Released on J-STAGE: April 18, 2017
    DOIhttps://doi.org/10.5575/geosoc.2016.0049
    JOURNAL FREE ACCESS
    Show abstractHide abstract

    The results of petrography and whole-rock major and trace element analyses of igneous rocks from Iheya North Knoll, middle Okinawa Trough, SIP Expedition CK14-04 (Exp. 907) are reported. During Expedition CK14-04, three holes were drilled for taking core samples: one at Site C9016 (Hole C9016B) and two at Site C9015 (Holes C9015B and C). Five pumice pebbles from Hole C9016B and three altered volcanic rocks from each of Holes C9015B and C9016B were analyzed. The pumices were essentially unaltered, and major and trace element compositions were similar to the literature values for middle Okinawa Trough rhyolites, except for Cu and Pb. The altered volcanic rocks appeared to be rhyolites based on microscopic core observations, and various degrees of silicification in terms of whole-rock geochemical composition were observed. Nevertheless, some of the altered rhyolites preserve igneous geochemical features that are similar to the overlying pumices and the middle Okinawa Trough rhyolites.

    View full abstract
    Download PDF (4291K)
Lecture
Excursion Guidebook
    • |<
    • <
    • 1
    • >
    • >|
feedback
 Top