Elisa Kagan Hebrew University of Jerusalem & the Geological Survey of Israel July 23, 2008 Hebrew University of Jerusalem (Ph. D advisors: Amotz Agnon, Moti Stein, Mira Bar-Matthews)
Paleoseismology is the study of the timing, location, and size of ancient earthquakes. San Andeas Fault, California
Interested in knowing: • Recurrence of earthquakes • Location • Magnitude • Local Intensities, site effects • Mechanisms • Segmentation • Fault interactions • Directivity • Etc…………. . TOOLS: • Instrumental Record • Historical Record • Paleoseismic Record (Faults, deformed sediments e. g. lake sediments, speleothems)
Instrumental is so precise! BUT… way too short Historical…. Quite detailed…. BUT, not totally reliable and also TOO SHORT (up to 2000 years) Long, detailed, and well-dated paleoseismic record needed 10’s-100’s of thousands of years v largest quakes may not be included in historical records v more seismic cycles v insight into long-term recurrence times and patterns (G&R, clustering…)
Surface rupture is recorded in the landscape and the sediments
Modeling $$$
Paleoseismic Data pre-instrumental caveats • Site specific • Data sets CAN be small, sparse, analog (changing in a continuous manner relative to another quantity ) • Quantification of uncertainty - major challenge
We need: • Earthquake-induced geological evidence (on-fault or off-fault) • Preserved evidence • Accessibility • Dateable material • Preferably continuous record • Preferably multi-site, multi-archive
Different paleoseismic techniques
Fault scarp created by the 1959 Hebgen Lake, Montana, earthquake
ON-FAULT STUDIES Trenching across faults Across Seattle Fault Bet Zayda (near the Kinneret) San Andreas, 1600 earthquake
ON-Fault: • Fault-specific • Can measure rupture • Can measure recurrence • Can differentiate different segments • Can interpret magnitude
Example Fault Database from California (CDMG) Need to “trench” each and every one!
Slip Rates (mm/yr) By Segment Very detailed information!
Average Recurrence Interval (years) At Measurement Sites
On-Fault not always available May be covered by soil, alluvium, lake, ocean This includes basically all subduction zone quakes (e. g. majority of devastating tsunami-triggering earthquakes) Japan: Fault scarp, hidden deep within a black spruce thicket. . .
PRO & CON: Can include evidence of earthquakes from various faults
TECTONIC SETTING Off-fault evidence can record earthquakes from various locations and distances
Paleo-tsunami deposits Chile
Jody Bourgeois
Fallen Boulders Kiryat Shemona MSc Mor Kanari
A stream channel offset by the San Andreas fault, Carrizo Plain, central California (photo by Robert E. Wallace) Geomorphology deformed landforms
Dendroseismology – tree-ring analysis, earthquake-damaged trees
New Madrid Seismic Zone -Intraplate
Clastic Dikes in Lisan Fm. , Ph. D - Zafrir Levy
Nahal Mishmar, Deformed Lake Sediment
Speleoseismology Soreq Cave (Bet Shemesh), Fallen Stalagmite
Nimrod crusader fortress offset Archaeoseismology Susita Ateret - Vadum Iacob - N. Wall
Cross correlation of data types: • Paleoseismicity • Plate tectonics • GPS • Instrumental
Modified Mercalli Intensity Scale עוצמה The real measure of the "badness" of the earthquake Based on human observations of damage and effects of earthquakes, not any measurement by a machine. • Gives a local characteristic of the earthquake at a site. • Based on response of people and structures. • MMI is generally larger near the epicenter of an earthquake, and decreases with distance. • However, site effects can cause anomalies in this trend.
examples: • IV. Felt indoors by many, outdoors by few. • Awakened few, especially light sleepers. Frightened no one, unless apprehensive from previous experience. Vibration like that due to the passing of heavy or heavily loaded trucks. Sensation like heavy body striking building or falling of heavy objects inside. Rattling of dishes, windows, doors; glassware and crockery clink and clash. Creaking of walls, frame, especially in the upper range of this grade. Hanging objects swung, in numerous instances. Slightly disturbed liquids in open vessels. Rocked standing motor cars noticeably.
• VIII. Fright general -- alarm approaches panic. • • Disturbed persons driving motor cars. Trees shaken strongly -- branches, trunks, broken off, especially palm trees. Ejected sand mud in small amounts. Changes: temporary, permanent; in flow of springs and wells; dry wells renewed flow; in temperature of spring and well waters. Damage slight in structures (brick) built especially to withstand earthquakes. Considerable in ordinary substantial buildings, partial collapse: racked, tumbled down, wooden houses in some cases; threw out panel walls in frame structures, broke off decayed piling. Fall of walls. Cracked, broke, solid stone walls seriously. Wet ground to some extent, also ground on steep slopes. Twisting, fall, of chimneys, columns, monuments, also factory stacks, towers. Moved conspicuously, overturned, very heavy furniture.
Modified Mercalli Intensity Map Borah Peak Earthquake Oct 28, 1983 Ms=7. 3
INQUA SCALE “A global catalogue and mapping of earthquake environmental effects" Using the present to interpret the past Calibrate the scale: modern, measured earthquakes & geological effects Then: use paleoseismic evidence and calibrate to magnitude etc… Request: report to them ALL geological effects after an earthquake
Damaged cave deposits as paleoseismological markers
Forti & Postpischl, 1984. Marine Geology Postpischl et al, 1991. Tectonophysics Lacave et al. , 2004 J. Earthquake Engineering Kagan et al. , 2005. Geology Gilli, 2005. Comptes Rendus Geoscience
Ø Seismological studies show enhancement of amplitudes (x 6 and more) may occur at depths (but also at times reduction) Ø due to interference of upcoming and downgoing waves (e. g. Bard and Tucker, 1985) Site effect is yet unknown
Soreq Caves
Location Map Eshtaol N Soreq Cave Beit-Shemesh Har-Tuv Cave To Jerusalem
*עבודות קודמות בנושא פלאואקלים, קארסט, והידרולוגיה במערת שורק: Asaf, 1975; Even, 1983; Frumkin et al. , 1994; Kaufman et al. , 1998; Ayalon et . 2002 , 1002, 0002, 9991, 7991, 6991, 1991 , . al. , 1998, 1999, 2002; Bar-Matthews et al • השקעה רציפה >185 kyr
• דמיון רב בין שתי המערות • התמוטטויות ותופעות נזק רבות • מיקום מאפשר רישום רעידות אדמה מהעתק ים המלח ואולי מהעתקים נוספים • סינון של רעידות קטנות
איך יודעים שרעידות אדמה גרמו לנזקים במערות אלו?
מה לא גרם לנזקים?
נזק אנתרופוגני? נזק מבעלי חיים? לא!! אין כניסות טבעיות!! חציבה רק במאה האחרונה תיארוך התופעות פותר את בעיית החציבה
פרמה-פרוסט? תנועת קרח? לא במרכז ישראל! תקופות קרח לא היו קרות מספיק ולא היה כיסוי קרח נהרות תת-קרקעים? השתפלות? לא היו במערות המחקר
אירועים אקלימיים? • לא נמצאה קורלציה עומס סטטי ? • רעידת אדמה תהיה ה"טריגר" • זקיפים גם נשברו
מה עשינו? * פיתוח השיטה * קביעת גילי התמוטטויות, והארכת הרקורד הקיים מ-07 ) ky מהליסן( ל-581 ky * קורלציה עם הרקורד הפלאוסייסמי הקיים • תרומה לרקורד הפלאוסייסמי של אזור המרוחק מההעתק הפעיל, רקורד של הרעידות הגדולות
• מיפוי • דיגום )בעיקר ע"י קידוח גלעינים( של כ-07 התמוטטויות, וזיהוי המגעים הפלאוסייסמיים • פיענוח • תיארוך בשיטת 230 Th/234 U • השוואה עם מחקרים פלאוסייסמים נוספים
מיפוי כיוונים מעודפים של ההתמוטטויות N
לפני התמוטטות אחרי התמוטטות
regrowth נפול
תקרות ממוטטות
שכבות של התמוטטויות במשקע זרימה )שמהווה את רצפת המערה( . 9991 , After Gilli
Collapse layers in flowstone שכבות של התמוטטויות במשקע זרימה Core in flowstone
~10 cm Pre-collapse Post-collapse חתך: נטיף נפול, לכוד במשקע זרימה
• תיארוך הלמינות מעל ומתחת למגע הפלאוסייסמי בעזרת איזוטופים רדיאואקטיביים - אורניום ותוריום ) (U/Th )מדידת האיזוטופים השונים בעזרת מס-ספקטרומטר(
דיוק בתיארוך רעידות אדמה )או כל אירוע גיאולוגי אחר( שגיאה אנליטית )שיטת התיארוך האבסולוטי( )שגיאה של % 2 -1 : ] (234 U/230 Th [MCICPMS שגיאה גיאולוגית: § קירבת הדוגמא למגע הפלאוסייסמי § מספר השנים שהדוגמא מייצגת )תלוי בגודל וקצב השקעה( § האם הגילים הם "מינימום" או "מקסימום" או שניהם )רווח? (
Fallen macaroni stalactites and fallen ceiling pieces embedded in floor flowstone lamina U/Th (Multi Collector) and d 18 O dating, PRE Z PRE MC= 53. 5 ± 1. 1 ky Y POST X Flowstone has slow growth rate usually W V MC= 82. 2 ± 1. 6 ky MC= 108. 1 ± 1. 7 ky MC= 129 ± 2. 8 ky Sample SO-57 U 2 U 1 T S POST PRE
Fast growth rate POST B=40. 1 ± 0. 2 ka PRE C=40. 9 ± 1. 4 ka BC Sample SO-1 -6
• דגימה: 07 התמוטטויות, • יותר מ-07 גילי MCICPMS • זמן חזרה של בערך 000, 01 שנה
שאלות / בעיות פתוחות 1. א. מהי עוצמת הסף המקומית לגרימת הנזק המתועד ומתוארך במערות? - פתרון ע"י ניסויים הנדסיים ותצפיות " "LIVE של השפעת רעידות אדמה עכשוויות 1. ב. ומכאן מהי המגניטודה המינימאלית הצפויה לגרום אותם נזקים? פתרון ע"י ניסויים אילו תגובות אתר ישפיעו על העוצמות המקומיות? )איזו מגניטודה תביא לאיזו עוצמה מקומית? (. . ומכאן מה המגניטודה הנדרשת?
מהי עוצמת הסף ? Threshold Intensity דוג' מצרפת 6991 2. 5 M נזק במערה 01 ק"מ מהמוקד, באזור עוצמה (MSK) VI בעיקר נטיפי קש שבורים כנראה היתה תגובת אתר בעקבות טופוגרפיה 9991 , . Gilli et al
Faulting & Paleoliquefaction in the Lisan Fm. Marco and Agnon, 1995; Marco et al, . , 1996; Agnon et al. , 2006
בקרקעית נוצר נוף מדורגת הרבדה
שלבים ביצירת שכבת רסק Breccia Layer
-b וניזול במים גלים יצירת -c הרחפה
-c הרחפה -d התרחיף ושקיעת
e השקעה המשך -
U-Th dating 70 000 year record Longest worldwide at the time 1996, JGR
Different sites show somewhat different records
Holocene lake sediment paleoseismology Nahal Ze’elim
Ken-Tor et al. , JGR, 2001; Ken-Tor et al. , Radiocarbon, 2001 ? 31 B. C. ? ? 64 B. C.
נחל צאלים -מחשוף outcrop Agnon et al. , 2006 Ken-Tor et al. , 2001
צאלים גם, אבל "עמוק", אין היאטוסים דוקטורט שלי
1997 coring campaign Migowski et al. , 2004
מבחן לשיטה עו צמ מגניטודה ה מק ומ ית מופיע בחתך מרחק נעדר בחתך
מרחק אפיצנטר ק”מ מגניטודה עו צמ ה מק ומ ית 6002 , . Agnon et al
במשך מפורט רישום שנה אלפים עשרת אנו חיים בתקופה פעילה 4002 , . Migowski et al
Identifying the Largest Earthquakes in Lisan Lacustrine Breccias by Correlation with Cave Seismites and Asphalt-bearing Breccias זיהוי רעידות האדמה החזקות ביותר ברקורד הסייסמיטים בתצורת ליסן ע"י קורלציה עם ספליאוסייסמיטים וברקציות המכילות אספלט 15, 000 -75, 000 yr BP Lake Lisan deformed varves Soreq Cave deformed speleothems
Late Pleistocene earthquake history of Dead Sea Basin and Judea Mt. area Documented by: Lake Lisan & stalagmite cave archives Massada Plain (M 1 b) Perazim Valley (PZ) Nahal Tovlan (NT) Nahal Tamar (TM) Nahal Mishmar (MR) Soreq Cave Searching for matching events in the different archives
compare seismites from various types of sediments & locations Lake Cave • Different number/type/thickness of seismites • Different number/type of seismites • Location, source distance • Water depth • Lithology • Sediment compaction • Slope & basin structure • Location, source distance • Depth underground • Size of cave room • Type of speleothem
Motivation Paleoseism records. Normally lucky to find one suitable site Records and recurrence rates are typically based on one site Multi-archive study : Ø different medium (dif. response to EQ) Ø different location (dif. distance to EQ) Ødifferent physical conditions (e. g. water depth) Øsite effects (amplification)
Dead Sea basin, central Dead Sea Transform sites (Modified after Garfunkel et al. , 1981)
Site locations Tovlan Soreq Caves Mishmar Massada Perazim Tamar Lisan maximum extent (LGM)
Soreq caves +400 m 60 m Dead Sea Transform 40 km (filters out smaller events) +200 m Sea level -200 m -400 m Lake Lisan levels LGM ~26 ka eg: 35 ka Perazim & Tamar Massada, Mishmar & Tovlan consequences for seismite formation eg: 46 ka
Lacustrine intraclast breccias SEISMITES (Marco, Agnon et al. 1995, 1996, 2005; Ken-Tor et al. , 2001; Migowski et al. , 2004; Agnon et al. , 2006; Kagan et al. , 2006) Brecciated, homogenated, folded, faulted
Association of Asphalt Inclusions and Breccias in Lisan
Association of Asphalt Inclusions and Breccias in Lisan • Observed in many sites • May represent asphalt or oil discharge into lake before strong earthquake • Turbulence after quake may cause floating asphalt/oil to be trapped in sediment before oxidation takes place Historical accounts of asphalt floating on Dead Sea after earthquakes (Arie Nissenbaum, 1977)
Methods (1) Field : Lacustrine section- detailed description, sampling for dating and chemical analysis Cave- core drilling & hand samples for dating and chemical analysis, description of seismites, spatial analysis (2) Chronology : U-Th on calcite cave deposits and on Lisan aragonite (MC-ICP-MS at Geological Survey of Israel) MC-ICP-MS
From these different and distant paleoseismic sites, three to four events stand out (~ 10% of total)
RESULTS Seismite speleoseismites 70 ka-15 ka - 27 damaged speleothems dated - Define minimum 6 tectonoseismic events
Findings Lisan Lake sediment field work and dating • Massada: 21 seismites, thinner seismites Massada • Perazim: 29 seismite ages recalculated, very thick seismites (data from Marco et al. , 2006; ages recalculated after Haase-Schramm et al. , 2004) • Tovlan: ONE seismite • Tamar: small part of section studied • Mishmar: 2/3 of entire Lisan (10 seismites, in period when PZ has 19 and M 1 b has 9) Tovlan
Massada - west Massada - east Nahal Tamar 34. 8 ka Mas-6 36. 2 ka (detrital Tas-24 contamination) 34. 8 ka Mas-3 32. 6 ka Tas-22 34. 1 ka Mas-1 RESULTS 38. 4 ka (ss) Mas-2 (preliminary) Legend Chronology of Asphalt in breccias aad layer breccia layer conglomerate asphalt 36. 2 ka Mas-4 34. 9 ka Tas-20 dating sample 38. 7 ka Mas-5 50 cm 36. 8 ka Tas-21 Schematic diagram of outcrops of asphalt-bearing breccia layers at Massada and Nahal Tamar, all yielding ages from approximately 33 to 39 ka. Ages given are isochron ages, except for the one marked ss (single sample).
Massada Section Additional Gypsum Unit Top Member The White Cliff Height (m) Broken Gypsum Unit Torfstein, Kagan, in progress Three Gypsum Unit Bottom Member Dating of Massada Lisan site (multi-sample isochrons) Almost complete Small Gypsums Unit Middle Member Gypsum 5 Samra-Lisan transition
COMPARISON RESULTS Soreq Cave Massada Perazim HIATUS Tovlan Tamar ABS: asphaltbearing seismites
Recurrence Interval IN LAKE & CAVE - 3 -4 earthquakes show at most sites in 55 kyr - 14 -18 kyr recurrence interval for the largest events expected for DST
Such long recurrence intervals are rarely reported in the literature, but probably because such long paleoseismic records have rarely been dated and most existing ones don’t actually include full seismic cycles. But according to Marco et al. , 1996: Mean recurrence interval for largest events: M 7. 9 is 50, 000 yrs M M 7. 5 is 20, 000 yrs May accommodate slip deficit Calculation: Assume Guttenberg Richter log 10 N = 2. 66 – 0. 93 M (from 1983 -1993 (Shapira & Shamir, 1994) According to the Lisan mixed layer record a M 6. 3 event will occur once in 1600 yrs and from here M 7. 9 is 50, 000 yrs and M 7. 5 is 20, 000 yrs
Summary & Conclusions 1. Differences in records can shed light on how different media and environmental conditions affect recording of earthquakes 2. Different locations and different media record earthquakes differently but the large earthquakes show through most medium 3. Asphalt Bearing Seismites may be ancient precursors to large earthquakes 4. Distinctive large earthquakes occurred at central DST at ~ 38 -40, 52, 71 ka 5. These are probably the largest earthquakes on the DST Work in Progress 1. Similar Analyses in Holocene Records 2. 2. Small-scale spatial analyses (on order of meters) of seismite variability 3. Lithological, grain-size analysis 4. Detailed analysis of lake levels correlation to seismite record
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