paleoseismology

Elisa KaganHebrew University of Jerusalem& the Geological Survey of Israel

July 23, 2008

(PhD advisors: Amotz Agnon, Moti Stein, Mira Bar-Matthews)

Hebrew University of Jerusalem

Paleoseismology is the study of the timing, location, and size of ancient earthquakes.

San Andeas Fault, California

plates

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 sedimentse.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 needed10’s-100’s of thousands of years

largest quakes may not be included in

historical records

more seismic cycles

insight into long-term recurrence times and

patterns (G&R, clustering…)

Surface rupture is recorded in the landscape and the sediments

$$$

Modeling

Paleoseismic Datapre-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

San Andreas, 1600 earthquakeBet Zayda (near the Kinneret)

Across Seattle Fault

ON-FAULT STUDIES

Trenching across faults

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!

At MeasurementSites

Average Recurrence Interval(years)

On-Fault not always available

May be covered by soil, alluvium, lake, ocean

Japan: Fault scarp, hidden deep within a black spruce thicket...

This includes basically all subduction zone quakes (e.g. majority of devastating tsunami-triggering earthquakes)

PRO & CON: Can include evidence of earthquakes from various faults

TECTONICSETTING

Off-fault evidence can record earthquakes from various locations and distances

Paleo-tsunami deposits

Chile

Jody Bourgeois

Fallen Boulders

MSc Mor KanariKiryat Shemona

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., PhD - Zafrir Levy

Nahal Mishmar, Deformed Lake Sediment

Soreq Cave (Bet Shemesh), Fallen Stalagmite

Speleoseismology

Archaeoseismology

Ateret - Vadum Iacob - N. Wall

Susita

Nimrod crusader fortress offset

Cross correlation of data types:

•Paleoseismicity

•Plate tectonics

•GPS

•Instrumental

Modified Mercalli Intensity Scale

• 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.

עוצמהThe real measure of the "badness" of the earthquake

Based on human observations of damage and effects of earthquakes, not any measurement by a machine.

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 and 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.

Borah Peak Earthquake

Oct 28, 1983

Ms=7.3

Modified Mercalli Intensity Map

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 effectsThen: 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

Seismological studies show enhancement of amplitudes (x6 and more) may occur at depths (but also at times reduction)

due to interference of upcoming and downgoing waves

(e.g. Bard and Tucker, 1985)

Site effect is yet unknown

Soreq Caves

Eshtaol

Beit-Shemesh

N

ToJerusalem

Soreq Cave

Har-Tuv Cave

Map bet-

shemesh

Location Map

עבודות קודמות בנושא פלאואקלים, קארסט, והידרולוגיה*  במערת שורק:

 Asaf, 1975; Even, 1983; Frumkin et al., 1994; Kaufman et al., 1998; Ayalon et al., 1998,1999,2002; Bar-Matthews et al., 1991,1996,1997,1999,2000,2001, 2002.

>kyr 185 רציפההשקעה •

דמיון רב בין שתי המערות•

התמוטטויות ותופעות נזק רבות•

מיקום מאפשר רישום רעידות אדמה מהעתק ים • ואולי מהעתקים נוספים המלח

של רעידות קטנות סינון•

איך יודעים שרעידות אדמה?גרמו לנזקים במערות אלו

?מה לא גרם לנזקים

נזק אנתרופוגני? נזק מבעלי ?חיים

לא!! אין כניסות טבעיות!!

רק במאה האחרונהחציבה

תיארוך התופעות פותר את בעיית

החציבה

anthropogenic

פרמה-פרוסט?

תנועת קרח?

לא במרכז ישראל!תקופות קרח לא היו קרות מספיק

ולא היה כיסוי קרחנהרות תת-קרקעים?

השתפלות?

לא היו במערות המחקר

Perma-frost

אירועים אקלימיים?

לא נמצאה קורלציה•

? עומס סטטי

רעידת אדמה תהיה •

ה"טריגר"

זקיפים גם נשברו•

תרומה לרקורד הפלאוסייסמי של אזור המרוחק מההעתק •הפעיל, רקורד של הרעידות הגדולות

* פיתוח השיטה

* קביעת גילי התמוטטויות, והארכת

185 (מהליסן) ל- 70kyמ- הרקורד הקיים

ky

קורלציה עם הרקורד הפלאוסייסמי * הקיים

מה

עשינו?

מיפוי •

)בעיקר ע"י קידוח גלעינים( של דיגום • התמוטטויות, וזיהוי המגעים 70כ-

הפלאוסייסמייםTh/234U230 בשיטת תיארוך • פיענוח•

עם מחקרים פלאוסייסמים נוספיםהשוואה •

Mapping

N

כיוונים מעודפיםהתמוטטויותשל ה

מיפוי

אחרי התמוטטות

לפני התמוטטות

diagrams

נפול

regrowth

נפול

regrowth

תקרות ממוטטות

שכבות של התמוטטויות במשקע

זרימה)שמהווה את

רצפת המערה(

After Gilli, 1999.

Collapse layers in flowstone

שכבות של התמוטטויות במשקע זרימה

Core in flowstone

Pre-collapse

Post-collapse

חתך: נטיף נפול, לכוד במשקע זרימה

~10cm

מעל ומתחת למגע הפלאוסייסמי בעזרת הלמינותתיארוך •איזוטופים

(U/Th) אורניום ותוריום - רדיאואקטיביים (מס-ספקטרומטר )מדידת האיזוטופים השונים בעזרת

דיוק בתיארוך רעידות אדמה )או כל אירוע גיאולוגי אחר(

)שיטת התיארוך שגיאה אנליטיתהאבסולוטי(

)234U/230Th [MCICPMS]: 1-2 % )שגיאה של

:שגיאה גיאולוגיתקירבת 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

U2

Sample SO-57

MC= 53.5 ± 1.1 ky

MC= 82.2 ± 1.6 ky

MC= 108.1 ± 1.7 ky

U/Th (Multi Collector) and d18O dating,

MC= 129 ± 2.8 ky

Y

X

V

W

Z

T

S

U1

PRE

PREPOST

POST

POST

PRE

PRE

Flowstone has slow growth rate usually

CB

POSTB=40.1 ± 0.2 ka PRE

C=40.9 ± 1.4 ka

Sample SO-1-6

Fast growth rate

התמוטטויות, 70 דגימה: • גילי 70 יותר מ- •

MCICPMS זמן חזרה של בערך •

שנה10,000

שאלות / בעיות פתוחות

המקומית לגרימת הנזק המתועד ומתוארך עוצמת הסף.א. מהי 1

במערות?

" של השפעת רעידות LIVE - פתרון ע"י ניסויים הנדסיים ותצפיות "

אדמה עכשוויות

הצפויה לגרום אותם נזקים?המגניטודה המינימאלית.ב. ומכאן מהי 1

- פתרון ע"י ניסויים

אילו תגובות אתר ישפיעו על העוצמות המקומיות? (איזו

מגניטודה תביא לאיזו עוצמה מקומית?).... ומכאן מה

המגניטודה הנדרשת?

Threshold Intensity ? מהי עוצמת הסף

1996דוג' מצרפת

M 5.2

VI (MSK) ק"מ מהמוקד, באזור עוצמה 10נזק במערה

בעיקר נטיפי קש שבורים

כנראה היתה תגובת אתר בעקבות טופוגרפיה

Gilli et al., 1999

Marco and Agnon, 1995; Marco et al,., 1996; Agnon et al., 2006

Faulting & Paleoliquefaction in the Lisan Fm.

בקרקעית נוצר נוף מדורגת הרבדה

שלבים ביצירת

שכבת רסק

Breccia Layer

b-וניזול במים גלים יצירתcהרחפה-

c- הרחפהd- התרחיף ושקיעת

e- השקעה המשך

1996, JGR

U-Th dating70 000 year recordLongest worldwide at the time

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., 2006Ken-Tor et al., 2001

2 sigma, until 8 meters depth

66

07

49

41

93

63

17

53

3

-14

0

-52

5

-75

0

14

56

y = -0.2946x + 472.14

R2 = 0.9829

0

100

200

300

400

500

600

700

800

900

-1500 -1000 -500 0 500 1000 1500

Age BC/AD

De

pth

, m

C14 calibrated ages

seismites, historicalcorrelation

Linear (C14 calibratedages)

צאלים גם, אבל "עמוק", אין היאטוסיםדוקטורט שלי

1997 coring campaign

Migowski et al., 2004

מבחן לשיטה

מגניטודה

מופיעבחתך

נעדרבחתך

עוצמה מקומית

קח

מר

Agnon et al., 2006עוצמה מקומית

מגניטודה

מק”

ר ט

צנפי

אק

חמר

במשך מפורט רישום שנה אלפים עשרת

אנו חיים בתקופה פעילה

Migowski et al., 2004

Identifying the Largest Earthquakes in Lisan Lacustrine Breccias

by Correlation with Cave Seismites and Asphalt-bearing Breccias

זיהוי רעידות האדמה החזקות ביותר ברקורד הסייסמיטים ע"י קורלציה עם ספליאוסייסמיטים וברקציות בתצורת ליסן

המכילות אספלט

Lake Lisan deformed varves

Soreq Cave deformed speleothems

15,000-75,000 yr BP

Late Pleistocene earthquake history of Dead Sea Basin and Judea Mt. area

Documented by: Lake Lisan & stalagmite cave archives

Massada Plain (M1b)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

• Different number/type/thickness of seismites

•Location, source distance •Water depth•Lithology•Sediment compaction•Slope & basin structure

Cave

• Different number/type of seismites

•Location, source distance •Depth underground•Size of cave room•Type of speleothem

Paleoseism records.

Normally lucky to find one suitable site

Records and recurrence rates are typically based on one site

Multi-archive study :

different medium (dif. response to EQ)

different location (dif. distance to EQ)

different physical conditions (e.g. water depth)

site effects (amplification)

Motivation

(Modified after Garfunkel et al., 1981)

Dead Sea basin, central Dead Sea Transform

sites

Lisan maximum extent (LGM)

Massada

Perazim

SoreqCaves

Tovlan

Tamar

Site locations

Mishmar

Sea level

+200 m

+400 m

-200 m

-400 m

Lake Lisan levels

Soreq caves

Massada, Mishmar & Tovlan

Perazim & Tamar

40 km (filters out smaller events)

60 m

consequences for seismite formation

Dea

d S

ea T

ran

sfo

rm

LGM ~26 ka

eg: 35 ka

eg: 46 ka

(Marco, Agnon et al. 1995, 1996, 2005; Ken-Tor et al., 2001; Migowski et al., 2004;Agnon et al., 2006; Kagan et al., 2006)

Lacustrine intraclast brecciasSEISMITES

Brecciated, homogenated, folded, faulted

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

Association of Asphalt Inclusions and Breccias in

Lisan

Historical accounts of asphalt floating on Dead Sea

after earthquakes

(Arie Nissenbaum, 1977)

(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)

Methods

MC-ICP-MS

From these different and distant paleoseismic sites, three to four events

stand out(~ 10% of total)

70 ka-15 ka - 27 damaged speleothems dated - Define minimum 6 tectonoseismic events

Speleoseismite age ranges

15 20 25 30 35 40 45 50 55 60 65 70 75

1000's of years

sam

ple

pre

post

RESULTSspeleoseismites

Sei

smit

e

Findings Lisan Lake sediment field work and dating

• Massada: 21 seismites, thinner

seismites

• 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 M1b has 9)Tovlan

Massada

Massada - west

38.4 ka (ss) Mas-2

34.8 kaMas-3

34.1 ka Mas-1

34.8 kaMas-6

36.2 kaMas-4

38.7 kaMas-5

Massada - east

36.2 kaTas-24

36.8 kaTas-21

32.6 kaTas-22

34.9 kaTas-20

Nahal Tamar

Legend

aad layer

breccia layer

asphalt

dating sample

conglomerate

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).

50 cm

RESULTS (preliminary)

Chronology of Asphalt in breccias

(detrital contamination)

3

6

9

12

15

18

21

24

27

30H

ei gh t ( m)

Top Gypsum Unit

The WhiteCliff

Three Gypsum Unit

Additional Gypsum Unit

Top

Mem

ber

Mid

dle M

emb

erB

ottom

Mem

ber

Samra-Lisan transition

Gypsum 5

Broken Gypsum Unit

Small Gypsums Unit

Massada Section

Dating of Massada Lisan site(multi-sample isochrons)

Almost complete

Torfstein, Kagan, in progress

RESULTS

Tovlan

Tamar

Perazim

Massada

Soreq Cave

HIATUS

COMPARISON

seismites

ABS: asphalt-bearing 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 Richterlog10N = 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. 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