まとめ
マグニチュード8.4を超える可能性がある大規模な地震を含む,大規模な潜水地域地震は,過去1700年間にわたり,カリフォルニア北部のハンボルト湾地域に影響を与え,重大な断層の移転と土地レベルの変化を引き起こしました.
科学分野:
- 地質学 地質学 地質学
- パレオシズモロジー (Paleoseismology) とは
- テクトニクス (地質学) とは
背景:
- ハンボルト湾地域は,ゴルダプレートと北米プレートの境界付近に位置し,構造的に活発です.
- 過去の大規模な地震がこの地域で発生しており,地震の危険性が高いという証拠があります.
研究 の 目的:
- ハンボルト湾地域における推力断層系におけるホロセンの古地震活動の調査.
- この地域における過去の大規模な地震のタイミング,強度,頻度を決定するためです.
主な方法:
- リトル・サーモンとマッド・リバーの断層地帯における移転したストラティグラフィックマーカーと断層オフセットの分析.
- 地質学的堆積物の放射性炭素 (炭素-14) 年代測定は,出来事の時間表を確立するためのものです.
- 断層現象と地域的な沈下および上昇指標との相関関係.
主要な成果:
- リトル・サーモンの断層では,過去1700年以内に3つの大きな移転 (それぞれ5〜7メートル) が起こった.
- マッド・リバー・フォールト・ゾーンでは,より少ない頻度で,より小さな移転が起こります.
- 沼地の泥炭の沈下,化石の森林埋葬,海洋テラス上昇の同期的なエピソードが,大規模な地震の発生を示しています.
結論:
- リトル・サーモンの断層の移転に関連した地震は,少なくともマグニチュード7.6-7.8.8であった.
- これらの事象は,ゴルダ・北米プレート境界の破裂を象徴し,8.4以上の潜在的な大きさを持つ可能性が高い.
- ハンボルト湾地域は,ホロセーン全体を通して,繰り返し発生する,大規模な沈殿地震地帯の地震を経験してきました.
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