Long‐Term Creep Rates on the Hayward Fault: Evidence for Controls on the Size and Frequency of Large Earthquakes
Long‐Term Creep Rates on the Hayward Fault: Evidence for Controls on the Size and Frequency of Large Earthquakes
复制标题
海沃德断层的长期蠕变率：控制大地震规模和频率的证据
DOI：
--
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
S. Caskey
中科院分区：
文献类型：
--
作者：
J. Lienkaemper;F. McFarland;R. Simpson;R. Bilham;D. Ponce;J. Boatwright;S. Caskey
加州的海沃德断层（HF）发生大地震（M w 6.5-7.1），重现时间较短（161±65年），可能因26%-78%的无震释放率（包括地震后）而保持较短。它的地震间释放率随时间的推移而局部变化，我们从几十年的表面蠕变数据推断。最早的估计蠕变率，主要是从不频繁的调查抵消文化功能，揭示了明显的空间变化率沿着故障，但没有检测到的时间变化。自1989年洛马普列塔6.9级地震（LPE）以来，通过32个水准仪和5个蠕变仪的监测，大大提高了蠕变率的时空分辨率。我们现在确定了显着的时间变化，主要与当地和区域地震。最大的速率变化是HF南端附近5 km长的蠕变沿着停止6年，归因于LPE的区域应力下降，1996年以2 cm蠕变事件结束。从1991年开始，在靠近联合城的北部，在断层的16公里长的范围内，利率明显比LPE前的水平高出25%。2007年奥克兰附近的一次Mw4.2地震引发了沿断层沿着10-15 km的1-2 cm蠕变事件。使用新的更好约束的长期蠕变率，我们更新了早期估计的沿HF沿着锁定的深度。锁定深度勾勒出一个单一的，约50公里长的锁定或延迟补丁的潜在M w 6.8事件相当于1868年HF地震。我们建议，这个推断补丁调节高频大地震的规模和频率。
在线资料：2007年事件蠕变模型、蠕变仪数据图、重新定位的微震和活动断层痕迹的地图和横截面，以及蠕变深度的迭代解。
The Hayward fault (HF) in California exhibits large ( M w 6.5–7.1) earthquakes with short recurrence times (161±65 yr), probably kept short by a 26%–78% aseismic release rate (including postseismic). Its interseismic release rate varies locally over time, as we infer from many decades of surface creep data. Earliest estimates of creep rate, primarily from infrequent surveys of offset cultural features, revealed distinct spatial variation in rates along the fault, but no detectable temporal variation. Since the 1989 M w 6.9 Loma Prieta earthquake (LPE), monitoring on 32 alinement arrays and 5 creepmeters has greatly improved the spatial and temporal resolution of creep rate. We now identify significant temporal variations, mostly associated with local and regional earthquakes. The largest rate change was a 6‐yr cessation of creep along a 5‐km length near the south end of the HF, attributed to a regional stress drop from the LPE, ending in 1996 with a 2‐cm creep event. North of there near Union City starting in 1991, rates apparently increased by 25% above pre‐LPE levels on a 16‐km‐long reach of the fault. Near Oakland in 2007 an M w 4.2 earthquake initiated a 1–2 cm creep event extending 10–15 km along the fault. Using new better‐constrained long‐term creep rates, we updated earlier estimates of depth to locking along the HF. The locking depths outline a single, ∼50‐km‐long locked or retarded patch with the potential for an M w∼6.8 event equaling the 1868 HF earthquake. We propose that this inferred patch regulates the size and frequency of large earthquakes on HF.
Online Material: 2007 event creep models, plots of creepmeter data, maps and cross‐sections of relocated microearthquakes and active fault traces, and iterative solutions for depth of creep.