備註請放最後面 違者新聞文章刪除
1.媒體來源:
外媒 phys.org
2.記者署名:
edited by Gaby Clark, reviewed by Robert Egan
3.完整新聞標題:
California's tectonic stress has reached record level, earthquake model
reveals
模型顯示加州地殼應力已創歷史新高!極限未知
4.完整新聞內文:
California's tectonic stress has reached record level, earthquake model
reveals
by University of Bern
edited by Gaby Clark, reviewed by Robert Egan
模型顯示加州地殼應力已創歷史新高!極限未知
伯恩大學 提供
由加比·克拉克 編輯 ，羅伯特·伊根審閱
https://i.urusai.cc/weVOK.jpg
Earthquakes usually occur along fracture zones in Earth's crust, where large
tectonic plates slide past one another and become locked. Stress builds up
over long periods and is suddenly released in the form of an earthquake. In
Southern California, the San Andreas and San Jacinto faults are among the
most significant of these zones, accommodating most of the plate motion in
the region.
Where the two fault systems approach each other northeast of Los Angeles lies
the Cajon Pass—a tectonically complex junction where a rupture on one fault
could potentially cross onto the other. Since the last major earthquake to
affect the wider Los Angeles region, the Fort Tejon earthquake of 1857, with
a magnitude of 7.9, tectonic stress along the fault segments has built up
continuously during a prolonged quiet period that has long concerned
researchers, given the potential for a large future rupture.
In a new study led by Dr. Liliane Burkhard of the Division of Space Research
and Planetary Sciences (WP) at the Physics Institute of the University of
Bern, an international research team modeled 1,000 years of earthquake
history along the southern San Andreas and San Jacinto fault systems to
estimate the present-day stress loading at Cajon Pass. Researchers from the
University of Hawai at Mānoa, the U.S. Geological Survey Earthquake
Science Center in Pasadena, and the Scripps Institution of Oceanography at UC
San Diego were involved.
地震通常發生在地球地殼的斷層帶，那裡大型構造板塊會相互滑動並相互鎖定。應力在長
期累積後突然以地震的形式釋放。在南加州，聖安德烈亞斯斷層和聖哈辛托斷層是其中最
重要的斷層帶，承載著該地區大部分的板塊運動。
在洛杉磯東北部，兩條斷層系統交會處是卡洪山口—一個構造複雜的交會點，一條斷層
的破裂有可能蔓延到另一條斷層上。自1857年震級為7.9級的特洪堡地震（上一次影響大
洛杉磯地區的大地震）以來，斷層段的構造應力在一段漫長的平靜期中持續積累，鑑於未
來可能發生大規模破裂，這長期以來一直令研究人員擔憂。
在伯爾尼大學物理研究所太空研究與行星科學部（WP）的莉莉安·伯克哈德博士領導的一
項新研究中，一個國際研究團隊模擬了聖安德烈亞斯斷層南部和聖哈辛托斷層系統沿線
1000年的地震歷史，以估算卡洪山口目前的應力負荷。參與這項研究的研究人員來自夏威
夷大學馬諾阿分校、美國地質調查局帕薩迪納地震科學中心、加州大學聖地牙哥分校史克
里普斯海洋研究所。
The results show that tectonic stresses in the region have reached and, in
some cases, exceeded the highest levels of the last millennium.
In the study, the researchers also introduced the concept of Cajon Pass as an
"earthquake gate," a junction that controls whether large earthquakes remain
confined to a single fault or propagate across both systems simultaneously.
The study has just been published in Journal of Geophysical Research: Solid
Earth.
結果表明，該地區的構造應力已經達標，並且在某些情況下超過了過去一千年來的最高水
平。
在這項研究中，研究人員也提出了卡洪山口作為「地震閘門」的概念，它控制著大地震是
局限於單一斷層還是同時跨越兩個斷層系統傳播。這項研究已發表在《地球物理研究期刊
：固體地球》。
Modeling 1,000 years of earthquake history
To investigate how stress along the San Andreas and San Jacinto faults and at
the critical Cajon Pass junction has evolved over time, the research team
constructed a physics-based, four-dimensional earthquake cycle model that
simulates processes in three spatial dimensions and over time. The
researchers then fed the model a 1,000-year earthquake record reconstructed
from geological evidence such as radiocarbon dating, tree-ring anomalies and
historical documentation of ground ruptures.
"The model tracks how each earthquake changes stress on neighboring fault
segments, how stress accumulates during the quiet intervals between events,
and how the deeper layers of the crust slowly relax following large
ruptures," Burkhard explains.
"This simulation allows us to understand how stresses in the fault system
build up over centuries," Burkhard continues. "By running the earthquake
history of Southern California as a simulation, we can estimate the extent to
which the fault system is already under stress today."
The researchers show that stresses in the region are currently at their
highest level in the last 1,000 years.
模擬1000年的地震歷史
為了探討聖安德烈亞斯斷層和聖哈辛托斷層以及關鍵的卡洪山口交匯處的應力如何隨時間
演變，研究團隊建立了一個基於物理學的四維地震週期模型，該模型能夠模擬三維空間和
時間維度上的過程。隨後，研究人員將根據放射性碳定年、樹木年輪異常和歷史地殼斷裂
記錄等地質證據重建的1000年地震記錄輸入到該模型中。
「該模型追蹤每次地震如何改變相鄰斷層段的應力，應力如何在地震事件之間的平靜期積
累，以及地殼深層在大破裂後如何緩慢鬆弛，」伯克哈德解釋。
「這項模擬使我們能夠了解斷層系統中的應力是如何在幾個世紀中累積起來的，」伯克哈
德繼續說道。 “透過模擬南加州的地震歷史，我們可以估算出斷層系統目前承受的應力
程度。”
研究人員表示，該地區目前面臨的壓力處於近1000年來的最高水準。
'Earthquake gate' as a decisive key factor
A key finding of the study is that the Cajon Pass can act as a so-called
"earthquake gate," a junction that controls whether large ruptures remain
confined to a single fault or cross both fault systems. Historical examples
of both behaviors exist: The Fort Tejon earthquake of 1857 terminated at
Cajon Pass and did not involve the San Jacinto Fault, while the Wrightwood
earthquake of 1812 ruptured through the junction and across both systems in a
single through-going event.
"The earthquake gate concept captures something important about how fault
junctions work," Burkhard explains.
"Cajon Pass doesn't simply block or channel earthquakes: It responds to
stress conditions, and those conditions change over centuries."
「地震閘門」作為決定性關鍵因素
該研究的一項關鍵發現是，卡洪山口可以起到所謂的「地震閘門」作用，它控制著大型地
震破裂是局限於單一斷層還是跨越兩個斷層系統。歷史上存在這兩種情況的例子：1857年
的特洪堡地震止於卡洪山口，並未涉及聖哈辛托斷層；而1812年的賴特伍德地震則穿過該
交匯處，在一次貫穿性地震中跨越了兩個斷層系統。
「地震閘門的概念捕捉到了斷層連接處運作方式的一些重要特徵，」伯克哈德解釋。
“卡洪山口並非簡單地阻擋或引導地震：它會對應力條件做出反應，而這些條件會隨著時
間的推移而變化。”
The study also shows that the decisive factor is not only how much stress has
built up on a single fault, but how aligned the stresses on the two fault
systems are. When the stress on both faults rises in concert over time,
toward similarly high levels, conditions favor a large joint rupture crossing
both systems. When stress levels evolve out of step with each other, ruptures
are more likely to terminate at the junction rather than propagate further.
Currently, modeled stress has reached 3.6 MPa on the San Jacinto-Bernardino
section, exceeding the highest value seen anywhere in the 1,000-year
simulation. On the neighboring Mojave South section of the San Andreas Fault,
it is 2.8 MPa. Both segments are therefore highly and relatively similarly
stressed, placing the system in a configuration that historically has
preceded joint ruptures.
"So not only is it concerning that the stresses are reaching historic highs,"
Burkhard says, "but also that the relative stress conditions between the two
fault systems are approaching the range we associate with major ruptures
crossing both faults simultaneously—and that is a scenario with much larger
consequences for the region."
研究還表明，決定性因素不僅在於單一斷層上累積的應力大小，還在於兩個斷層系統上的
應力是否一致。當兩個斷層上的應力隨時間同步上升至相似的高水準時，有利於形成橫跨
兩個斷層的大型節理破裂。而當應力水準變化不一致時，破裂更有可能在交會處終止，而
不是進一步擴展。
目前，模擬應力在聖哈辛托-貝爾納迪諾斷層段已達到3.6兆帕，超過了1000年模擬中任何
位置的最高值。在鄰近的聖安德烈亞斯斷層莫哈韋南段，應力為2.8兆帕。因此，這兩個
斷層段都處於較高且相對接近的應力狀態，使該系統處於歷史上節理破裂發生的先兆狀態
。
“因此，令人擔憂的不僅是應力達到了歷史最高水平，”伯克哈德說，“而且兩個斷層系
統之間的相對應力條件正接近我們所說的同時跨越兩個斷層的重大破裂的範圍—這種情
況對該地區的影響要大得多。”
Increased risk in densely populated regions
A joint rupture of the San Andreas Fault and the San Jacinto Fault that
crosses the Cajon Pass would be a much more severe event than one limited to
a single fault. The affected region includes some of the most densely
populated, infrastructure-critical corridors in the U.S., including the
greater Los Angeles area, San Bernardino, Riverside and the Coachella Valley.
Major highways, railroads and energy infrastructure run through the Cajon
Pass itself.
"The question of when and how the next major earthquake will occur in this
region is one of the most pressing problems in applied geoscience. Our
results provide a clearer, physics-based picture of the current stress state
of the fault system, and the framework we developed is applicable not just to
California, but also to other complex fault junctions worldwide," Burkhard
says.
However, Burkhard emphasizes: "The study is not a prediction of when an
earthquake will occur. What we can say is that the system is critically
stressed and that physics-based models like ours give a clearer picture of
the range of scenarios we should be prepared for. This information is
important for hazard assessment, infrastructure planning, and emergency
preparedness."
人口稠密地區風險增加
聖安德烈亞斯斷層和橫跨卡洪山口的聖哈辛托斷層同時斷裂，其後果將遠比單一斷層斷裂
嚴重得多。受影響區域包括美國人口最稠密、基礎設施最為關鍵的走廊地帶，例如大洛杉
磯地區、聖貝納迪諾縣、河濱縣和科切拉谷。主要公路、鐵路和能源基礎設施均穿過卡洪
山口。
「下一次大地震何時以及如何發生在這個地區，是應用地球科學領域最緊迫的問題之一。
我們的研究結果從物理學的角度更清晰地展現了斷層系統當前的應力狀態，我們建立的框
架不僅適用於加利福尼亞州，也適用於世界各地其他複雜的斷層交匯處，」伯克哈德說。
然而，伯克哈德強調：“這項研究並非預測地震何時發生。我們只能說，該系統正處於臨
界壓力之下，而像我們這樣的基於物理的模型能夠更清晰地展現我們應該做好準備應對的
各種情景。這些信息對於災害評估、基礎設施規劃和應急準備至關重要。”
5.完整新聞連結 (或短網址)不可用YAHOO、LINE、MSN等轉載媒體:
https://reurl.cc/V2Vgl6
6.備註:
不知道是南極還是加州的地圖會先重畫？
https://i.urusai.cc/qwWln.jpg