地学雑誌 | Journal of Geography (Chigaku Zasshi)

2013 Vol.122 No.3

Subducting Philippine Sea Plate beneath the Tokyo Metropolitan Area being Torn into Two Parts, with One Part being Left behind to the East

(Front) Map showing S-wave velocity distribution along a curved surface located 10km above the Pacific plate (Nakajima and Hasegawa, 2010). The color scale shows S-wave velocities. The contact zone between the Pacific and Philippine Sea plates is enclosed by two thick broken lines. Red stars denote five M 7-class earthquakes that have occurred in southern Kanto since 1885. Beach balls show the focal mechanisms of the 1921 M 7.0 Ryugasaki earthquake (two solutions shown) and the 1987 M 6.7 east off Chiba earthquake. Black circles represent aftershocks of the 1987 earthquake.
(Back) Serpentinized mantle of the Philippine Sea plate at its easternmost portion (shaded in brown). The dashed pink line represents the approximate location of the western boundary of the serpentinized mantle. Grey broken contour lines show depths to the upper surface of the Philippine Sea plate. Green squares and circles plot interplate earthquakes on the upper surface of the Pacific plate, and gray dots plot earthquakes in the mantle of the Philippine Sea plate. Beach balls also show the focal mechanisms of four earthquakes in the mantle of the Philippine Sea plate. The purple circle denotes an aftershock (M 7.1) of the 1923 Kanto earthquake that occurred ∼30h after the main shock. The Philippine Sea plate is being torn into two parts along the dashed pink line: the easternmost portion of the serpentinized mantle subducts at a slower rate, having been left behind the western part, the trunk of the Philippine Sea plate. The pink ellipse denotes a seismic gap pointed out by Okada and Kasahara (1990).

(Akira HASEGAWA)

Review Articles

Geological Predictions for the Long-term Isolation of Radioactive Waste Based on Extrapolating Uniform Mode and Rate of Crustal Movements

Koji UMEDA, Shin-Ichi TANIKAWA and Ken-Ichi YASUE

Journal of Geography (Chigaku Zasshi), 2013, 122(3), 385.

DOI:10.5026/jgeography.122.385

Subduction of Two Oceanic Plates and Unique Seismic Activity beneath the Tokyo Metropolitan Area

Akira HASEGAWA, Junichi NAKAJIMA, Naoki UCHIDA and Norihito UMINO

Journal of Geography (Chigaku Zasshi), 2013, 122(3), 398.

DOI:10.5026/jgeography.122.398

Original Articles

Farmers' Adaptation Strategies to Changes in Agri-tourism in the Nishino Area, Minami-Alps City, Yamanashi Prefecture

Takuya HAYASHI

Journal of Geography (Chigaku Zasshi), 2013, 122(3), 418.

DOI:10.5026/jgeography.122.418

Relationships between Global Climate Indices and Rain-fed Crop Yields in Highland of South-Central Java, Indonesia

Bayu D.A. NUGROHO, Ardiansyah O.D. PRIMA, Hiromitsu KANNO, Ryoji SAMESHIMA, Hiroshi FUJII and Larry C.M. LOPEZ

Journal of Geography (Chigaku Zasshi), 2013, 122(3), 438.

DOI:10.5026/jgeography.122.438

Processes of Terrace Formation and Crustal Movement during the Late Quaternary on the West Coast of Ise Bay

Daisuke ISHIMURA

Journal of Geography (Chigaku Zasshi), 2013, 122(3), 448.

DOI:10.5026/jgeography.122.448

Effects of Sedimentary Depositional Environment on the Dynamic Mechanical Properties of Holocene Clay in the Southern Kanto Plain, Central Japan

Takato TAKEMURA, Masanobu ODA, Shoichiro HAMAMOTO, Ken KAWAMOTO, Tomoya AKAMA, Hidemichi TAI and Katsumi KIMURA

Journal of Geography (Chigaku Zasshi), 2013, 122(3), 472.

DOI:10.5026/jgeography.122.472

Short Articles

An Assessment of the Magnitude of the AD1586 Tensho Tsunami Inferred from Lake Suigetsu Sediment Cores

Megumi SAITO-KATO, Kazuyoshi YAMADA, Richard A. STAFF,Takeshi NAKAGAWA, Hitoshi YONENOBU, Tsuyoshi HARAGUCHI,Keiji TAKEMURA and Christopher BRONK RAMSEY

Journal of Geography (Chigaku Zasshi), 2013, 122(3), 493.

DOI:10.5026/jgeography.122.493