History and Future of Seismologyby

Peter Bormann(formerly GFZ Potsdam)

Rebeur-Ehlert pendulum, 1895 KSJ, 1990 | ← 8 cm →|

TSJ-1

|← 25 cm →|

1. Earliest reports about earthquakes and their causes

1831 BC First report from China, Province Shantung→ „Shaking of the Taishan Mountain“

After 780 BC Since Chou Dynasty in N-China very detailedwritten reports which allow reconstruction of damage and → intensity estimates

Old Testamony Book of Zacharia: First correct description of an observed strike-slip left-lateral motion on theDead Sea fault

Thales of Milet Earth swims on the universal ocean.(624-556 BC) → the motion of its waters causes earthquakes

Anaximenes Rock masses fall into caves or other void(585-525 BC) spaces of the Earth

→ causes earthquake sounds and shaking

Anaxagoras Fire within the Earth´s interior(500-428 BC) → primary cause of earthquakes

Aristotel • there is a central fire in the Earth(384-322 BC) • subsurface caves and galleries cause fire

as storm clouds cause lightning• rapidly expanding underground fires produce

rumbling and shaking when meeting obstacles

• Places with bad underground are shakenmore severe since they contain much „wind“

• subsurface and atmospheric processes areinterconnected

• There are vertical and horizontal EQ motions!

Aristotel´s explanation was widely accepted/repeatedfor more than 2000 years until the 17th/18th century AD!

Seneca „Quaestiones naturalis“(4 BC – 65 AD) Air passing through underground galaries and

void space causes earthquake shaking.Compressed air may trigger wild subterraneousstorms leading to widepread damage whenthey brake through to the Earth´s surface.

Chang Heng First known seismoscope132 B.C

Model of the Chang Hengseismoscope in Tangshan,China (Photo: P. Bormann)

2. Descriptions of EQs and their causes in our times (AD)

René Descartes • „Principia Philosophiae“ (1644), (1596-1650) part 3: „About die Earth“

• Sketches the stages of the developmentof the Earth and its various spheres:

E – outer Earth´s crust, consisting of clay, sand, mud, rocksC – innermost Earth´s crust, consisting of metals; D – water;F – thinned room, M – dense dark matter, I – sun/light matter

• Sub-soil burning of oil/petroleum is considered to bethe cause for earthquakes and volcanism

Athanasius Kirchner „Mundus Subterraneae“ (1678)

Japanese medieval folkloreattributes EQs to naughtyjumping monster catfishes

Desperate people, frightened bythe Earth´s shaking, try to quiettwo jumping monster catfishes.

A monster catfish, responsible for thelast disaster EQ is punished by the supreme God for his naughtiness in front of other catfishes, who were responsible for earlier EQs, so as to remind them to stay quiet.

Scientific rational behind it:Catfishes are extremely sensitive tochanges in the Earth´s electric fieldas caused by breaking quartz crystalsin EQ ruptures. Catfish have indeed been observed to jump out of the water desperately prior to/during EQs.

1750 Referend Stephen Hales took up these ideas in explaning two EQsin London:

„Ascending sulphuric gases in the Earth´s interior may catch fireand thus cause Earth´s lightenings. Their explosion is the directcause for earthquakes

1746 J. G. Krüger´s „Geschichte der Erde in den allerältesten Zeiten“

• Exothermal reaction of pyrite (sulphur and iron) with water and self-ignition of sulphuric and other explosive gases and burnablematerials in the Earth´s may result in huge subsurface fires andexplosions and are the cause for earthquakes, volcanic eruptions,faulting, folding and tilting of Earth´s layers, the formation offractures and void spaces in the Earth and play a role in the formation of oceans and continents.

• Volcanoes are very useful, because they allow these explosive gases and subsurface fires to escape. Thus they reduce the riskof excessive pressures build-up and prevent even more frequentcatastrophic earthquakes.

1755, November 1st: Lissabon earthquake and tsunami

• Some 50,000 people killed and 15,000 houses damaged• Up to 30 m high tsunami wave in Tejo river mouth• Tsunami still noted on shores of England, France and Germany

The Lissabon EQ triggered a fierce debate about the causesof EQs between clerics and intellectuals in Europe:

1756 Johann Michael Wagner:„God determines the essence and controls the effects of nature accordingto his intentions. He accompanies the execution of his will with rewardand the neglectance of it with punishment….He directs the natural eventsin the ways in which they have to execute his revanche.“

1756/57 Immanuel Kant(1724 -1804)

• In view of so much human suffering this disaster should help us in developíng love and solidarity with the victims instead of seeing it as a conse-quence God´s revanche for man´s misdeeds.

• Endless numbers of bad people die in peace.

• EQs do shake some countries ever since, …the Christian Peru as much as the pagan Peru, while other cities never experienced such disasters since their earliest days although itspeople are not better than those in other cities.

In his two publications about the Lisbon EQ Immanuel Kant

• disproves, on the basis of Newton´s gravitation laws, that cometsand planets could generate strong earthquakes

• propagates Krüger´s ideas about the causes of earthquakes

• assumes an ocean bottom shaking and rapid uprise of some15 feet in an area with the side length between Cape St. Vincent andCape Finisterre as the cause of the strong tsunami. He calculates itspropagation according to the rules of hydrodynamics. The resultsagreed well with the observations.

• infer the existence of very extended submarine mountain chainsoutranging by far those known from the land surface and associatesthe Lisbon EQ with the submarine Azores ridge.

• mentions the observation of EQ precursory phenomena such asunrest of animals, sea level and water level changes in wells, changesin the spring water flow and lightning discharges.

1783 Calabria EQ: „Various effects of the 1783 earthquake near Settizano and Cossoletto in Calabria“

One of the first objective depictions of tectonic earthquake effects.

John Mitchel • describes in 1760 wave-like vibrations of two EQs(1724-1793) in London

• suggests calculation of wave speed by comparisonof arrival times at two well separated points

• calculates for the Lisbon EQ in 1755 0.5 km/s.

Charles Lyell • Develops the „Principle of Actualism“(1797 – 1875) in geological developments

• Visits after the New Zealand earthquake 1855the Windy Point/Rurakirae Head, at the southcoast of the Northern Island. There the EQ hadcaused coastal uplift between 2 m and 6.5 m.

• Concludes that all coastal mountains in thearea are due to repeated coastal uplifts in conjunction with large Pleistocene EQs.

Confirmation of the „Principle of Actualism“

Robert Mallet • Irish engineer; writes after field investigations of the(1810 – 1881) EQ near Napels on 16 Dec. 1857:

„The First Principles of Observational Seismology“

• Pioneered the application of physical and engineering principles to the explanation of the geologic nature of EQs;

• Defined several still valid notions in seismology, such as EQ focus, epicenter, hypocenter;

• First modern EQ catalogue with information aboutlocation, time and damages of EQs;

• First determination of source depth for Naples EQ (h = 10.4 km)

• Concludes that EQ waves are similar to sound waves andtravel with different velocity through different materialsdepending on their different physical properties;

• In 1880 foundation of the Seismological Society of Japan

• In 1851 first use of dynamite explosions in England tomeasure speed of elastic waves → explosion seismology

• In 1860 first world seismicity map published

Mallet´s 1890 world seismicity map based on reported felt EQ shaking alone

3. Scientific-technical findings and developments ofcrucial importance for the advancement of seismology

1678 Hooke, Robert Hooke´s law: Proportionality between stress and(1635 -1703) strain in elastic bodies

1691 Halley, Edmont Proposes an Earth´s model with a liquid outer(1656 -1742) and a solid inner core

1799 Cavendish, H. Determination of average density of the Earth(1731 -1810)

1821 Navier, Claude. L. General equations of elasticity(1785 -1703)

1822 Cauchy, A. L. Foundations of the theory of elasticity;(1789 -1836) Definition of terms stress, deformation etc.

1830 Poisson, S. D. Oscillations of an elastic sphere calculated;(1781 -1840)

First theoretical description of longitudinaland transverse waves;

Poisson ratio, Poisson distribution (EQ statistics)

1845 Stokes, George Definition of bulk and shear modulus(1819 -1903)

1841 Pagani portable pendulum seismometer

1856 First use of Palmieri´s „sismografo elettro-magnetico“ in the volcanicObservatory on Mount Vesuvius. The instrument responded to both verticaland horizontal motions and gave give direction, intensity and duration of EQs

From Earthquake Information Bulletin, Vol. 11, No. 2, 1979

1873/75 Suess, Eduard Hypothesis: EQs are bound to tectonic faults(??)

1874 De Rossi presents first widely used seismic intensity scale

1878 De Rossi builds first seismograph

Ernst Heinrich Bruns(1848-1919) „Theory of the figure of the Earth“

1880 Milne and Ewing First widely used seismographs

Milne record of a strong local EQ at Tokyoin 1882. The usefulness of Milne´s instrumentwas diminished by its lack of damping.

Principle of the MILNE seismograph.

Ewing´s horizontal pendulum seismometer and recordof a strong local earthquake on March 8, 1881.

1886 Brassart three-component seismometrographrecording on smoked paper and glas

1886 Brassart seismic warning device

1887 Rayleigh, Sir John W. Book „Theory of Sound“; proof of the(1842 -1919) existence of „Rayleigh“ LR surface waves

1888 Schmidt, August First description of the basic phenomena(1840 -1929) of the propagation of seismic waves

Wave fronts W

← Seismic rays S

← Travel-time curve

← Deflection point P depending on source depth

identifies in 1889 more than 30 transient eventsof different duration and amplitude which super-pose his long-period tidal records. He finds thatthey are often in close timely co-incidence in thesynchronous records at POT and WHF .

First records of an EQsat teleseismic distance →

E. v. Rebeur-Paschwitz(1861-95)

Tokyo EQ 1889

To ≈ 10 – 20 sV up to 295 times

Peter Bormann

1895 In the year of his death, there appear two major publications byE. v. REBEUR-PASCHWITZ in GERLAND´s Beiträge zur Geophysik,in which he states:

• There are surface and body waveswhich propagate through the Earth; →

• The propagation velocity is significantlylarger at greater depth than near tothe Earth surface;

• Accordingly, the apparent horizontalvelocity is a function of distance!

Therefore

Peter Bormann

→ „EQ observations provide us ... with a means to determine theelasticity modulus of the Earth interior at different depth.“

→ „We will thus be in a position, particularly with strongearthquakes, to track the wave propagation through thewhole Earth´s body and thus to develop the fundamentalsfor a new theory which will guide us, in an indirect way,gradually to the knowledge of the composition of theEarth´s Interior.“

In conclusion v. Rebeur-Paschwitz („Beiträge zur Geophysik, 2, p. 773-782):

• drafts a related resolution for the 6th International GeographicConvention held in London in 1895:

• proposes the establishement of an international system ofearthquake stations (in total 35)

Peter Bormann

• „We wish to propose in the first line the foundation of an international netof earthquake stations with the task to observe, in a systematic way, thepropagation of motions on the Earth´s surface and through the Earth bodythat emanate from large earthquake centers.“

• „It is desirable and for the success of this undertaking important that allstations select the same kind of instruments and that these are brought upto the same degree of sensitivity.“

• „All signatories consider a Central Bureau forthe collection and publicationof the earthquakereports from all over the world a necessarysupplement to the proposed monitoring system.“

This resolution is submitted to the conference byGeorg C. K. GERLAND (1833-1919) →Professor of Geography at Strasbourg University.

Reinhold Ehlert assistant with Georg GERLAND, modifies in 1896(1871-1899) the single-component horizontal pendulum of Ernst

v. REBEUR-PASCHWITZ to a 3-component horizontal pendulum, recommended byG. GERLAND as standard pendulum for theproposed global network ↓

1896

J. Emil Wiechert first German Professor of Geophysics at Göttingen(1861-1928)

1896 proposes that the Earth´s core consists of iron.1900 builds his first seismographs1903 publishes „Theory of automatic seismographs“

1904 astatic WIECHERT pendulum(N, E), T ≈ 8.5 s, V ≈ 200

WIECHERT 15 t pendulum, T = 2.2s, V = 2000

Richard D. Oldham Identifies P, S and L waves(1858-1936) in seismic records of the

Assam earthquake, India andsuspects possible existanceof an Earth´s core.

1897 Cancani (Italy) developed a 300 kg seismograph and records the strongAssam earthquake in India

Vicentini´s microseismograph

1899 First investigations into the energy of reflected and refractedseismic waves by Knott

Rudolph Straubel develops in Jena a vertical component seismographs(1864-1946) with high magnification and photographic registration

One out of world-wide only four recordsof the famous 1908 Tunguska meteoritefall with the Straubel vertical seismograph

1901

GERLANDWIECHERT

HELMERT

STRAUBEL

OMORI

First

The conference proposed an International Association for Seismology witha Permanent Commission, a General Assembly and a Central Bureau

1904 Foundation of the International Seismological Association (ISA)with its Central Bureau in Strasburg. → First Chairman: G. Gerlandt

1900 World maps of seismicity distribution by Montassus de Balloreand John Milne

1902 First global Earth´s modelpublished in Berlin

1905Boris B. Golizyn First electrodynamic seismograph with

(1862-1916) galvanometric recording

The Jena-built verticalcomponent seismometerof type Golizyn (Ts = 10 s)

the 1905 Cambridge-built horizontal componentGolizyn seismometer

Omori´s 60-secondhorizontal pendulum

1905 Ludwig Geiger Method for epicenter location of EQs based on(1882-1966) P-wave first arrivals

1906

Karl Zoeppritz compiles first teleseismic travel-time curves for(1881-1908) longitudinal, transversal body waves and surface waves

1906

H. F. Reid proposes after the 1906 San Francisco EQ the shear fracture/rebound hypothesis for tectonic EQs

R. D. Oldham infers fromworld-wide travel-timeobservations of P- and S-waves the existanceof a liquid Earth´s core

1907 Several innovative seismographsproduced by Agamemnone in Italy

Andrija Mohorovičič Discovers 1909 the lower boundary of the Earth´s(1857-1936) crust (Moho = Mohorovičič discontinuity)

Mohorovičič´s original travel-time graphand related crustal cross section (redrawn)

1910 Gustav Herglotz Develops 1910 (with E. Wiechert) first exact(1811-1953) procedure to derive 1-D velocity distribution

in the Earth´s interior from continuous seismictravel-time curves

1911 A.E.H. Love Theoretical proof of the existence of horizontallypolarized surface waves (Love waves)

1912 Mercalli-Cancani-Sieberg 12-degree seismic intensity scale

1913 Beno Gutenberg Determines depth of the core-mantle boundary(1889-1960) (2900 km)

G. becomes a pioneer of modern seismology:• finds with Richter (1944) the Gutenber-Richter law

(frequency of occurence of EQs as a function of magnitude)• develops teleseismic magnitude calibration

functiions for body and surface waves (1945)• discovers the asthenosphere (1948)

Alfred Wegener First publication of „The Origin of the Continents“(1880-1930) and Oceans“ in 1915

180 Mioyears B.P.

50 Mioyears B.P.

In 50 Mioyears A.P.

Internat. Geophysical Year

Upper Mantle Project

Geodynamic Project

1917/18 First studies of the mechanism of earthquakes by Shidain Japan, based on the azimuthal distribution of P-wavepolarities

Ludger Mintrop • Discovers 1919 critically refracted head-waves from(1880-1956) seismic discontinuities („Mintrop waves“; patented)

• Introduced already in 1908 the exploration of theuppermost Earth´s layers with controlled seismicsources (4t weight dropped from 14 m high skaffold)and portable seismometers

1922 First hints by H.Turner to the existence of EQs at large depth

1923 Nakano gives a physically plausible description of theearthquake by a point source model (quadrupol)

1923 B. Gutenberg publishes a first 1-D model of P- and S-wavevelocity distribution in the Earth based on teleseismicbody wave travel times

1926 Harald Jeffreys Proof that (outer) Earth´s core is liquid(1902-1993) and that the core-mantle boundary is a

compositional boundary (iron rocks)

1928 Kiyoo Wadati Proof of the existence of deep earthquakes(1902-1993) („Benioff-Wadati Zone“ subduction zones)

1935 Charles Richter Development of the first magnitude scale(1900-1985) assessing earthquake size from instrumental

recordings

Ml = logAmax - logA0

1935 Hugo Benioff Develops the first(1899-1968) strain meter

1936 Inge Lehmann Discovers the inner core of the Earth(1888-1993) and determines its radius with 1,400 km

Calculated byB. Gutenberg

Harald Jeffreys(1891-1989)

1940 Birch Hypothesis, that the Earth´s inner core consists ofsolid iron.

Presents, together with Bullen, first precise modelsof the Earth´s deep structure derived from theJeffreys-Bullen travel-time curves

1939-40

1939 Griggs is the first to assume convection currents in theEarth´s mantle as a mechanism to explain tectonic activities/mountain building

1950-53 Thomson and Haskell develop the matrix formalism for calcu-lating wave propagation through horizontally layered media

1952 Hugo Benioff records for the first time extremely long-periodseismic waves with periods around 57 min. He suspects thatthese are fundamental modes (free oscillations) of the Earth.

1956 Vvedenskaya´s hypotheses of the equivalence between forcesand dislocations in describing seismic source processes.

1958 Pekeris calculates theoretically spheroidal and toroidal eigenmodes of the Earth.

1957-59 First International Geophysical Year (IGY)

1960 The Chile Mw = 9.5 „Century earthquake“First clear observations of the Earth´s fundamental modes!

1960s • Deployment of the World-wide Standard SeismographNetwork (WWSSN) with sensitive SP and LP seismographs

• About 100 more stations with standardized SP, BB and oftenalso LP seismographs were deployed in the Soviet Union,East European states, Cuba and China

• Significantly improved global EQ detection and location

• Begin of routine determination of seismic fault-plane solutionsto derive main stress directions

Typical instrumentation used in the WWSSN:

Benioff

SP

Sprengnether

LP

Willmore SP

Geotech LP

Typical instrumentation used in the Soviet and East European network:

HSJ-I Ts = 15-30s

VSJ-ITs = 15-30s

VSJ-II Ts ≈ 1s

HSJ-II Ts ≈ 1s

Kirnos LP

Teupser LP

Teupser SP

And new types of sensors such as:

• borehole seismometers

• ocean bottom seismometers

• electronic seismometers

1960-69 International Upper Mantle Project (UMP)1970-79 International Geodynamic Project (IGP)

Elaboration of the seafloor spreading and plate tectonic concept

Essential steps and results:

Paleomagnetic pole positions fromCambrium to Trias-Jura

Paleomagnetic seafloor patterns of alternatingpolarities and paleomagnetic time scales(Vine and Mathew, 1963; Hertzler, 1966, et al.)

Ocean bottom topography from echo sounding

Details of echo sounding results whichstrongly support the concepts ofseafloor spreading and lithopheresubduction near deep sea trenches

(Ewing and Ewing, 1967, et al.)

Wilson´s hypothesis of transform faults existing along offsets of oceanic ridges (1965) proved by L. Sykes (1967) with detailedsource mechanism data.

Peculiarities of seismic source mechanismsin subduction zones (Isacks & Molnar, 1969)

From here onwards the presentation is not yet completed

Barazangi & Dorman (1969)