{"_buckets": {"deposit": "d98fd68d-372d-4ec4-b1a9-b8987341e1dc"}, "_deposit": {"id": "2800", "owners": [1], "pid": {"revision_id": 0, "type": "depid", "value": "2800"}, "status": "published"}, "_oai": {"id": "oai:nied-repo.bosai.go.jp:00002800", "sets": []}, "author_link": [], "item_10001_biblio_info_7": {"attribute_name": "書誌情報", "attribute_value_mlt": [{"bibliographicIssueDates": {"bibliographicIssueDate": "2006-02-01", "bibliographicIssueDateType": "Issued"}, "bibliographicIssueNumber": "1-3", "bibliographicPageEnd": "118", "bibliographicPageStart": "98", "bibliographicVolumeNumber": "150", "bibliographic_titles": [{"bibliographic_title": "Journal of Volcanology and Geothermal Research", "bibliographic_titleLang": "en"}]}]}, "item_10001_description_5": {"attribute_name": "抄録", "attribute_value_mlt": [{"subitem_description": "Iwo-jima is a volcanic caldera located 1250 km south of Tokyo, and is part of the Izu-Ogasawara arc. An extremely high uplift rate (averaging 0.25 m/a over several hundred years) characterizes the volcanic activity of Iwo-jima. This deformation is believed to be due to post caldera uplift. To investigate the mechanisms contributing to the high uplift rate, we have repeatedly conducted leveling and trilateration surveys from 1976 to 1995, and GPS surveys from 1996 to 2002. These observations have detected two patterns of continuous crustal deformation: Concentric subsidence around Motoyama at the center of the Iwo-jima caldera and uplift surrounding the subsiding area. During the period from 1977 to 1995, subsidence at Motoyama reached 0.54 m and uplift in the southwestern part of the island exceeded 3 m. In addition, the island has experienced broad, episodic uplift, which amounted to more than 1 m during volcanic unrest both in 1982 and 2001. Horizontal displacements around Motoyama exhibit contraction due to the concentric subsidence, indicating the presence of a deflating source at depth. Vertical deformation dominates the displacement field during periods of broad episodic uplift, suggesting a deeper and/or more extensive source. Focusing the Motoyama area, we modeled the subsidence source simultaneously with the broad episodic uplift, which is approximated by deformation with a planar gradient, for 14 times between 1976 and 2002, using a grid search combined with a least-squares method. By assuming the subsidence source could be located at any grid point, we applied the least-squares method to calculate the intensity of subsidence source and the parameters for the uplift with a planar gradient and then selected the best-fitting source location. The best-fitting subsidence source geometries for 1998-2000 and 2000-2002 (the two time periods with GPS results) are horizontal, squared-shaped sills with side lengths of 4 and 5 km, respectively. Adopting the horizontal sill with a side length of 4 km as the deflating source, we applied this model to the 12 additional measurement epochs. Stable solutions for the source were obtained for 8 of the 12 periods. The results indicate that the deflating source is located beneath the Motoyama area with a depth ranging from 0.1 to 2.4 km over time. The average rate of sill closing from 1976 to 2002 was 0.46 ± 0.32 m/a. Our analysis also quantified the episodic broad uplift, though the available data do not permit modeling of the source of the continuous uplift surrounding the subsidence area. Considering the density structure in the caldera, the continuous subsidence and uplift may be explained by movement of volcanic fluids (probably geothermal) to balance the vertical load of the volcano, while the episodic uplift appears to be related to magmatic unrest. c 2005 Elsevier B.V. All rights reserved.", "subitem_description_language": "en", "subitem_description_type": "Other"}]}, "item_10001_relation_14": {"attribute_name": "DOI", "attribute_value_mlt": [{"subitem_relation_type_id": {"subitem_relation_type_id_text": "10.1016/j.jvolgeores.2005.07.008"}}]}, "item_10001_source_id_9": {"attribute_name": "ISSN", "attribute_value_mlt": [{"subitem_source_identifier": "0377-0273", "subitem_source_identifier_type": "ISSN"}]}, "item_creator": {"attribute_name": "著者", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "M. Ukawa", "creatorNameLang": "en"}]}, {"creatorNames": [{"creatorName": "E. Fujita", "creatorNameLang": "en"}]}, {"creatorNames": [{"creatorName": "H. Ueda", "creatorNameLang": "en"}]}, {"creatorNames": [{"creatorName": "T. Kumagai", "creatorNameLang": "en"}]}, {"creatorNames": [{"creatorName": "H. Nakajima", "creatorNameLang": "en"}]}, {"creatorNames": [{"creatorName": "H. Morita", "creatorNameLang": "en"}]}]}, "item_language": {"attribute_name": "言語", "attribute_value_mlt": [{"subitem_language": "eng"}]}, "item_title": "Long-term geodetic measurements of large scale deformation at Iwo-jima caldera, Japan", "item_titles": {"attribute_name": "タイトル", "attribute_value_mlt": [{"subitem_title": "Long-term geodetic measurements of large scale deformation at Iwo-jima caldera, Japan", "subitem_title_language": "en"}]}, "item_type_id": "40001", "owner": "1", "path": ["1670839190650"], "permalink_uri": "https://nied-repo.bosai.go.jp/records/2800", "pubdate": {"attribute_name": "PubDate", "attribute_value": "2023-03-30"}, "publish_date": "2023-03-30", "publish_status": "0", "recid": "2800", "relation": {}, "relation_version_is_last": true, "title": ["Long-term geodetic measurements of large scale deformation at Iwo-jima caldera, Japan"], "weko_shared_id": -1}