Slide 1: What have we Learnt on Earthquakes and Volcanic Eruptions over the Last Years?
What have we Learnt on Earthquakes and Volcanic Eruptions over the Last Years? Nikolai Shapiro nikolai.shapiro@univ-grenoble-alpes.fr • CNRS, Institut de Science de la Terre, Université Grenoble Alpes, France • Geophysicist/seismologist with more than 30 years of experience in France, USA, Mexico, R
Slide 2: A few words about seismic/volcanic hazard and risk
A few words about seismic/volcanic hazard and risk Hazard is the physical loading from natural phenomena, i.e., ground shaking, tsunami wave, volcanic ash fall … Vulnerability id the degree of damage caused by various levels of loadings Risk is expressed in terms of economic cost , loss of lives or
Slide 3: Distribution of earthquakes and volcanoes
Distribution of earthquakes and volcanoes 3
Slide 4: Earth's interior structure and dynamics
Earth’s interior structure and dynamics Mantle convection heat sources: - decay of radioactive elements - heat left over from Earth's formation very slow process: mantle flow ~ cm/year 4
Slide 5: Plate tectonics
plate tectonics surface manifestation of mantle convection relative plate motion results in mechanical stresses and faulting within the outer layer of the Earth, the lithosphere, which is cool enough to behave as a more or less rigid shell 5
Slide 6: Challenges with understanding global seismic and volcanic cycles
Challenges with understanding global seismic and volcanic cycles Ideal “full” solution: complete physical model of the whole Earth, i.e., very heterogeneous and non-stationary dynamic system with a 4.5*109 years history and a ~5*108 years convection cycle conceptual representation Our observations a
Slide 7: Distribution of earthquakes and volcanoes
Distribution of earthquakes and volcanoes conceptual representation of a subduction zone melting More than 90% of earthquakes and volcanoes occur in subduction zones 7
Slide 8: Physical concepts of earthquakes and volcanoes
Physical concepts of earthquakes and volcanoes Earthquakes Volcanoes Frictional sliding and stick-slip Melting, magma migration and At first order – mechanical process differentiation, degassing … Complex mechanical and chemical processes 8
Slide 9: Earthquakes as a "stick-slip" phenomena
Earthquakes as a “stick-slip” phenomena 9
Slide 10: Earthquakes as a "stick-slip" phenomena: Seismic cycle
Earthquakes as a “stick-slip” phenomena Seismic cycle earthquakes average recurrence time 10
Slide 11: Observation of earthquakes
Observation of earthquakes Fault scarps can be observed for a few strong and shallow earthquakes 2002 Denali earthquake, Alaska For most of earthquakes, instrumental observations are needed 11
Slide 12: Observation of earthquakes
Observation of earthquakes Seismologicalc data: records of the motion of the Earth’s surface by seismographs • Regular seismic records started at the end of 19-th century • Till 1980s most of instrument had “analogous” recording system (low quality) • In 1990s continuous digital records started to b
Slide 13: Size of an earthquake is characterized by magnitude M
Size of an earthquake is characterized by magnitude M ML = log10A + 2.76 log10D - 2.48 Richter, 1935 13
Slide 14: Earthquakes sizes and magnitudes
2004 Sumatra earthquake Magnitude M = 9.1, rupture area >105km2 Earthquakes sizes and magnitudes Typical M = 5 earthquake ruptures area of a few km2 Rupture length ~ 1300 km Rupture speed ~ 2 km/s Earthquake duration ~ 10 min 14
Slide 15: Earthquakes sizes and magnitudes: M = log S + const
2004 Sumatra earthquake Magnitude M = 9.1, rupture area >105km2 Earthquakes sizes and magnitudes Typical M = 5 earthquake ruptures area of a few km2 M = log S + const magnitude rupture area 15
Slide 16: Gutenberg-Richter law (1935)
Gutenberg-Richter law (1935) log N = a – b M earthquakes between 1955 and present Earthquakes are planar objects (occur on fault planes) data from: https://earthquake.usgs.gov/earthquakes/search/ global catalog Natural geometrical characteristics of the size is: surface of ruptured fault area S M>9
Slide 17: Magnitude and damage
Magnitude and damage Effect of an earthquake is not simply related to its size Earthquakes with 1,000 or More Deaths 1900-2014 2010 Haiti Earthquake M = 7.0 > 300000 deaths 1960 Chile Earthquake M = 9.5 ~2000 deaths 17 https://earthquake.usgs.gov/earthquakes/world/world_deaths.php
Slide 18: 1960 Chile Earthquake M = 9.5
1960 Chile Earthquake M = 9.5 (largest known earthquake) Rupture mainly below the sea No big cities nearby in 1960-s 18
Slide 19: 2010 Haiti Earthquake M = 7.0
2010 Haiti Earthquake M = 7.0 Occurred on a shallow fault just below the main city Poor constructions 19
Slide 20: Level of earthquake shaking is characterized by macroseismic intensity
Level of earthquake shaking is often characterized by macroseismic intensity ground acceleration : physical parameter closest to macroseismic intensity 20
Slide 21: Seismic hazard
Seismic hazard In general terms, the seismic hazard defines the expected seismic ground motion at a site (phenomenon that may result in destructions and losses). Two major approaches – deterministic and probabilistic – are used for seismic hazard assessment. The deterministic approach takes into acc
Slide 22: Seismic hazard
pid GLOBAL SEISMIC HA: RD MAP 16 mooERATE | HAZARD| 22
Slide 23: Distribution of earthquakes and volcanoes
Distribution of earthquakes and volcanoes 23
Slide 24: Seismic hazard: some important questions
Seismic hazard Some important questions: • do we miss possible seismogenic faults? • could we underestimate maximum magnitudes? • are earthquakes predictable (should the hazard be time-variable)? 24
Slide 25: Earthquake seismology timeline
Earthquake seismology timeline 1875 First seismographs Main concepts of earthquake seismology were formulated and applied by the end of 1980-s. 1894 Omori’s law What is changing since? 1935 First Magnitude scale • rapidly growing vulnerability (population, infrastructure) 1949 Gutenberg Richter law
Slide 26: Major earthquakes (M>9) and what is changing
earthquakes between 1955 and present global catalog Main concepts of earthquake seismology were formulated and applied by the end of 1980-s. What is changing since? • rapidly growing vulnerability (population, infrastructure) • growing application of paraseismic building codes • more data (exponenti
Slide 27: Importance of secondary hazards such as tsunami
Main concepts of earthquake seismology were formulated and applied by the end of 1980-s. What is changing since? • rapidly growing vulnerability (population, infrastructure) • growing application of paraseismic building codes Importance of secondary hazards such as tsunami • more data (exponential g
Slide 28: Damage due to seismic motion alone was relatively small
Main concepts of earthquake seismology were formulated and applied by the end of 1980-s. The damage due to seismic motion alone What is changing since? was relatively small (<2%), in spite of the large magnitude of the earthquake. • rapidly growing vulnerability (population, infrastructure) • growin
Slide 29: Some important questions
Some important questions: • do we miss possible seismogenic faults? • could we underestimate maximum magnitudes? • are earthquakes predictable (should be the hazard time-variable)? Main concepts of earthquake seismology were formulated and applied by the end of 1980-s. What is changing since? • rapi
Slide 30: Require geological observations: paleoseismology
M=9 earthquake and was not expected in Japan M~8 earthquakes were observed instrumentally no significant difference in terms of ground shaking … dramatic underestimation of tsunami recurrence time of a M=9 earthquake is close to 1000 years require geological observations: paleoseismology 30
Slide 31: Non-instrumental observations: paleoseismology
non-instrumental observations: paleoseismology 31
Slide 32: Non-instrumental observations: paleoseismology
non-instrumental observations: paleoseismology 32
Slide 33: What is the value of absolute maximum magnitude?
What is the value of absolute maximum magnitude? Is this 9+, as already observed? probably YES Are 10+ earthquakes possible? probably NO thickness of the brittle seismogenic part of the Earth’s lithosphere is limited fault dimensions for a 10+ earthquake: fault width exceeding ~100 km and/or fault l
Slide 34: Can we go beyond stick-slip description?
Some important questions: • do we miss possible seismogenic faults? • could we underestimate maximum magnitudes? • are earthquakes predictable (should be the hazard time-variable)? Can we go beyond stick-slip description? Main concepts of earthquake seismology were formulated and applied by the end
Slide 35: "Slow" earthquakes
Rogers and Dragert, 2003 “Slow” earthquakes • considered by many as a major recent advance in physics of seismic cycle • new type of precursory phenomena • different physical models suggested • current observations/understanding are insufficient for applications in forecasting and hazard assessment
Slide 36: Space geodesy, plate motion, and earthquake recurrence
Space geodesy, plate motion, and earthquake recurrence measured motion of GPS sites plate motion model 2011 Japan earthquake • maximum slip on the fault > 70 m • plate convergence rate 9 cm/year • recurrence interval > 800 years 36
Slide 37: Some conclusive remarks about earthquakes and seismic cycle
Some conclusive remarks about earthquakes and seismic cycle • still no robust prediction algorithms despite many observed precursors • conceptually well understood • main loading (plate motion) is reasonably quantified • hazard is well characterized with some caveat about secondary hazards (tsunami,
Slide 38: Physical concepts of volcanoes
Physical concepts of volcanoes All representations of the volcano interior you can found are “cartoons” and we still do not really know its configuration and functioning information from analysis of erupted rocks • initial magmas are generated by melting in the mantle (~100 km depth) • they slowly r
Slide 39: More than 1500 volcanoes active during last 10,000 years
There are more than 1500 volcanoes that has been active during last 10,000 years on the surface of the Earth 39
Slide 40: More than 500,000,000 people live near potentially active volcanoes
More than 500,000,000 people leave in vicinity (< 100 km) of potentially active volcanoes 40
Slide 41: Ongoing volcanic activity
Ongoing volcanic activity 41
Slide 42: Some well-known catastrophes caused by explosive volcanic eruptions
Some well-known catastrophes caused by explosive volcanic eruptions Vesuvius in AD79: destructed of Pompeii and Herculaneum; killed more than 10,000 people Mount Pelée in 1915: killed 30,000 people 42
Slide 43: A recent effusive eruption: La Palma 2021
A recent effusive eruption: La Palma 2021 43
Slide 44: Volcanic hazards are difficult to assess
Volcanic hazards are difficult to assess Volcanic hazard are mostly estimated locally for relatively Multiple dangerous phenomena well studied volcanoes • lava flows Global hazard models are difficult to compile and validate • pyroclastic flows • lahars • landslides • debris avalanches • tephra or a
Slide 45: Air travel disruption after the 2010 Eyjafjallajökull eruption
Air travel disruption after the 2010 Eyjafjallajökull eruption Composite map of the volcanic ash cloud spanning 14–25 April 2010 • 107,000 flights cancelled during April 15-23 2010 • 48% of total air traffic and roughly 10 million passengers • total loss for the airline industry ~ US $1.7 billion 45
Slide 46: 2022 Hunga Tonga eruption
2022 Hunga Tonga eruption 650 km diameter after 1 hour 46
Slide 47: Volcanoes and magmatic reservoirs are volumetric objects
Volcanoes and magmatic reservoirs are volumetric objects This is natural to characterize eruptions with erupted volume V 47
Slide 48: Volcanic Explosivity Index and eruption size distribution
Volcanoes and magmatic reservoirs are volumetric objects This is natural to characterize eruptions with erupted volume V Logarithmic scale of eruption sizes Volcanic Explosivity Index (VEI) VEI = log V + 5 (for volume in km3) Probability of an eruption can be expected to be inversely proportional to
Slide 49: Catalog of volcanic eruptions available online
Catalog of volcanic eruptions available online • Huge effort of the volcanology community • Extends to pre-historic times • Provides a base for statistical analysis • VEI values are highly uncertain • Timing of eruptions is very approximate • No detailed time histories available for catalogued erupt
Slide 50: Eruption size distribution: Tambora, Pinatubo
1000 1200 1400 1600 1800 2000 whole smitsonian catalog ‘ b=1 10? « e . Fe 3 a D 5 10 3 10° é : ; : 5 i = ; : Vel
Slide 51: Pinatubo, Hunga-Tonga, St Helens
Pinatubo Hunga-Tonga St Helens b=1 51
Slide 52: Some critical questions
Some critical questions • Do we have reliable observations of the impact of major (VEI 6+) eruptions on modern infrastructure? NO • Are major (VEI 6+) eruptions possible in populated/developed regions? YES • What are maximum possible eruptions (Dragon Kings)? 52
Slide 53: Laacher Sea volcano VEI=6 eruption 13,000 years ago
Laacher Sea volcano VEI=6 eruption 13,000 years ago 53
Slide 54: 1815 eruption of Mount Tambora, Indonesia
1815 eruption of Mount Tambora, Indonesia • volcano height decreased from 4300 m to 2850 m • ejected up to 150 km3 of ashes • ~10,000 people were killed directly by the eruption • ~80,000 people died in Indonesia from deceases and starvation • ~200,000 people died in Europe because of the famine cau
Slide 55: Supervolcanic eruptions
Supervolcanic eruptions ; r Lake Toba @ (Indonesia) Krakatau (Indonesia) ‘Supervolcanoes are capable of producing e@ Lake Taupo ‘eruption that ejects more than (New Zealand) 1,000 cubjc kilometers of matter ‘The largest volcanic eruptions in hana history and iy the last million years {given in cubic
Slide 56: Toba super-eruption 74,000 years ago
Toba super-eruption 74,000 years ago 2800 km3 ≈ 2800 km2 covered by 1 km of volcanic ash • one of the Earth's largest known explosive eruptions • ejected ~2800 km3 of erupted material • possibly caused a global volcanic winter of six to ten years • possibly caused a 1,000-year-long cooling episode •
Slide 57: World changing eruptions
World changing eruptions erupted volumes > 106 km3 57
Slide 58: Some conclusive remarks about volcanic eruptions
Some conclusive remarks about volcanic eruptions • time predictable but not size predictable • physics still not sufficiently understood • main loading (magma production rate) is very poorly quantified • hazards are multiple and difficult to quantify • volcanic hazard should be considered as a globa
Slide 59: Thank you! Questions?
Thank you! Questions? 59
Slide 60: Many aviation flight corridors pass near active volcanoes
Many aviation flight corridors pass in the vicinity of active volcanoes 60
Slide 61: Some important questions: is earthquake occurrence random?
Some important questions: • do we miss possible seismogenic faults? • could we underestimate maximum magnitudes? • are earthquakes predictable (should be the hazard time-variable)? global M = 7+ earthquakes is the earthquake occurrence a random process? or : • is it clustered in time? • correlated w
Slide 62: Aftershocks and foreshocks
Aftershocks and foreshocks 62
Slide 63: Aftershocks and Omori's law (1894)
Aftershocks (release of the mainshock induced stress) Omori’s law (1894) 63
Slide 64: Aftershocks and foreshocks
Aftershocks and foreshocks Aftershocks • systematically observed • well described by statistical models (Omori’s, ETAS, …) • can be used for short-term hazard assessment? Foreshocks • precursory phenomena • intermittent (are not systematically observed) • cannot be robustly used for forecasting 64