Introduction

This earthquake analysis is based on the Global Significant Earthquake Database (GSED) and the NCEI/WDS Global Historical Tsunami Database hosted in the National Oceanic and Atmospheric Administration (NOAA) website.

The GSED is a global list of the most significant earthquakes. In order to be classified as a significant earthquake, the event must meet at least one of the following criteria: moderate damage (approximately $1 million or more), 10 or more deaths, magnitude 7.5 or greater, Modified Mercalli Intensity X or greater, or the earthquake generated a tsunami.

If the earthquake was associated with a tsunami or volcanic eruption, it is flagged and linked to the related tsunami event or significant volcanic eruption. However, due to the very complexity of tsunami events, and because they are not always related to earthquakes but also to volcanic eruptions, landslides, or any combination of these; the tsunami dataset provides these detailed data and more, which is not found in the earthquake dataset. Therefore, all tsunami data visualizations presented in this project are based on the tsunami dataset.

So, the GSED is an earthquake dataset of 6,344 entries and 38 columns (variables), and the tsunami dataset contains 2,809 entries and 45 columns (both until December 2023).

The following analysis is a voluntary work that will be updated at the beginning of each month, which also emphasizes the analysis of the previous 12 months. And, the purpose of this project is to present a visual and simple analysis to anyone who is interested in knowing more about worldwide earthquake and tsunami events.

Objectives of this analysis

  1. Analysis of the last twelve months to date
  2. Visualization map of earthquakes and tsunamis of the last 12 months
  3. Strongest earthquakes and tsunamis overall
  4. Deadliest earthquakes and tsunamis overall
  5. Earthquakes, number of deaths, and tsunamis per year
  6. Earthquakes and tsunamis by magnitude
  7. Summary of earthquakes by magnitude ranges
  8. Correlation between magnitude and focal depth
  9. Countries with most earthquakes and tsunamis
  10. Deadliest earthquakes and tsunamis by country
  11. Interactive world map for the earthquake dataset, color coded, and with magnitude filters
  12. Interactive world map for the tsunami dataset, color coded, and with magnitude filters

Earthquakes data concepts

Seismologists study earthquakes by looking at the damage that was caused and by using seismometers. A seismometer is an instrument that records the shaking of the Earth’s surface caused by seismic waves. The term seismograph usually refers to the combined seismometer and recording device.

Since the energy released by an earthquake travels in a wave, and earthquakes are actually recorded by a seismographic network, there are many different ways to measure different aspects of an earthquake. Magnitude is the most common measure of an earthquake’s size, and is also a measure of the amount of energy released. The Moment Magnitude is considered the most accurate scientific scale (the Richter’s scale developed in 1935 is an outdated method that is no longer used for large earthquakes). Also, the magnitude does not depend on where the measurement is made.

Earthquakes of magnitude 6 and above are the ones for concern. When nearby, they can cause shaking intensities that can begin to break chimneys and cause considerable damage to the most seismically vulnerable structures, such as non-retrofitted brick buildings.

Because of the logarithmic basis of the magnitude scales, each whole number increase in magnitude represents a tenfold increase in measured amplitude. This means that, at the same distance, a magnitude 9 earthquake produces vibrations with amplitudes 10 times greater than one of magnitude 8, and 100 times greater than one of magnitude 7 –as measured on seismograms–.

But the magnitude scale is really measuring the physical size of the earthquake, and not its strength (energy), because each whole number increase in magnitude also represents a release of energy 32 times greater. Thus, in terms of energy, the same earthquake of magnitude 9 releases about 32 times more energy (10**1.5 = 31.62) than an earthquake of magnitude 8 –and 1,000 times more energy than an earthquake of magnitude 7–. Since it is the energy or strength that knocks down buildings, this is really the more important comparison. This means that it would take 1,000 magnitude 7.0 earthquakes to equal the energy released by one magnitude 9.0! (USGS Reference).

However, in the end, the amplitude numbers are neater and a little easier to explain, which is why those are used more often in publications. But, it’s the energy that does the damage.

On the other hand, intensity scales like the Modified Mercalli Scale with valid values from 1 to 12 (see Appendix A) measure the amount of shaking at a particular location. An earthquake causes many different intensities of shaking in the area of the epicenter where it occurs. So, the intensity of an earthquake will vary depending on where you are. The Mercalli Scale is based on observable earthquake damage. The GSED provides the Modified Mercalli (MMI) Intensity when available.

So, from a scientific standpoint, the magnitude scale is based on seismic records while the Mercalli’s scale (see Appendix A) is based on observable data which may be subjective.

Magnitude Scale

Magnitude Effects
Less than 3.5 “Minor/micro” earthquake. Recorded on local seismographs, but generally not felt.
3.5 to 5.4 “Light” earthquake. Often felt, but rarely cause damage.
5.5 to 6.0 “Moderate” earthquake. At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings over small regions.
6.1 to 6.9 “Strong” earthquake. Can cause damage to poorly constructed buildings and other structures in areas up to about 100 kilometers across where people live.
7.0 to 7.9 “Major” earthquake. Can cause serious damage over larger areas.
8.0 to 8.9 “Great” earthquake. Can cause serious damage and loss of life in areas several hundred kilometers across.
9.0 to 9.9 “Rare Great” earthquake. Can cause major damage over a large region over 1000 km across.

The study period starting in 1900 was chosen because of the amount and accuracy of data available (earthquake magnitudes prior to 1890, the year in which the first seismographs began to be used, have been estimated by looking at the physical effects plus the human effects, and comparing them to modern earthquakes). So, the base data files used for this analysis contain earthquakes and tsunamis filtered since 1900 only.

Analysis and Visualizations

Full Disclosure:

All analyzes and visualizations that follow are valid in the context of the GSED dataset, as hundreds of earthquakes occur each month around the world, but not all meet the NOAA criteria for inclusion on the GSED list. However, other entities may list them differently, and using different criteria.

To get started, below is a comparative table of the amount of data analyzed from 1900 to date. The number of tsunamis listed here were taken from the tsunami dataset rather than the earthquake dataset because it lists more events (since not all tsunamis are earthquake related).

1. Analysis of the last twelve months to date

The purpose of the following 12-month analysis is to stay on top of the latest seismic events and visualize their data. Also, at the end of this section is a summary of some relevant data on last year’s earthquakes.

The bar graph below shows in order the total number of earthquakes for each month. In turn, the magnitude value is written in descending order for each earthquake within the column for each month. Besides, the magnitude values are color coded according to the legend shown on the right hand side.

The months are arranged in chronological order from left to right.

The bar graph below shows in descending order from the current month the total number of deaths for each month. In turn, the number of earthquakes for each month is color-coded according to the legend shown on the right hand side. The number of deaths for each month is written either inside of the bar or next to it. If in any month the length of the bar is null, this is because the number of deaths is 1. In these cases, consult the previous graph to find out the number of earthquakes for that month, since it cannot be determined here by the color of the bar.

The following is a cross-reference chart of months and countries, with the number of total earthquakes written inside the box. To facilitate visualization, each month has its own color according to the legend shown on the right hand side.

The months are arranged in chronological order from left to right.

The bar graph below shows in descending order the total number of deaths for each country. This number is written either inside or next to the country bar, and is also color coded according to the legend shown on the right hand side.

The following two visualizations are basically the same, they contain the same information but are arranged from two different perspectives: The first, according to the number of deaths; and the second, according to the magnitude values.

So, the bar chart below breaks down the number of earthquakes by country, with the magnitude value followed by the number of deaths written inside each segment (representing an earthquake). This chart is arranged from top to bottom in descending order by the total number of deaths for each country. In turn, within each country, earthquakes are also arranged in the same descending order from right to left. Further, the number of deaths is color coded according to the legend shown on the right hand side.

And events where the number of deaths is unknown or not available (NA) are colored in light yellow.

Finally, the next bar chart breaks down the number of earthquakes by country, with the magnitude values preceded by the number of deaths written inside each segment (representing an earthquake). This chart is arranged from top to bottom in descending order by the maximum magnitude values for each country. In turn, within each country, earthquakes are also arranged in the same descending order from right to left. Further, magnitude values are color coded according to the legend shown on the right hand side and, in this graph, all magnitude values are known.

On the other hand, some of the most relevant data from the previous visualizations are compiled and summarized below.

Summaries of Previous Years:

The following images are snapshots taken from the 2022 and 2023 year-end analysis summaries:


2. Visualization map of earthquakes and tsunamis of the last 12 months

The following two-layer world map is a supplemental visualization for the analysis above.

Hovering the mouse cursor on a colored icon displays a label, and clicking or tapping on it opens a text box containing more data about this specific event.

The icons are custom made for this project. They are coded with “T” for tsunamis and “Q” for earthquakes followed by their magnitude range. The date follows the format dd/mm/yyyy.

The “Earthquakes” layer also contains earthquakes that caused tsunamis, while the “Tsunami” layer includes tsunamis caused by earthquakes, landslides, volcanic eruptions, or any combination of these 3 events. The dark-cyan icon showing the letter “T” only represents non-earthquake tsunamis.

3. Strongest earthquakes and tsunamis overall

The following table is presented in descending order of magnitude.

The 20 strongest earthquakes/tsunamis
Magnitude Intensity Year Tsunami Volcanic Country Total Deaths
9.5 12 1960 Yes Yes CHILE: PUERTO MONTT, VALDIVIA 2,226
9.2 10 1964 Yes NA ALASKA 139
9.1 NA 2011 Yes NA JAPAN: HONSHU 18,428
9.1 NA 2004 Yes NA INDONESIA: SUMATRA: ACEH: OFF WEST COAST 227,899
9.0 7 1952 Yes NA RUSSIA: KAMCHATKA PENINSULA 10,000
8.8 9 2010 Yes NA CHILE: MAULE, CONCEPCION, TALCAHUANO 558
8.8 9 1906 Yes NA ECUADOR: OFF COAST 1,000
8.7 6 1965 Yes NA ALASKA: ALEUTIAN ISLANDS: RAT ISLANDS NA
8.6 NA 2012 Yes NA INDONESIA: N SUMATRA: OFF WEST COAST 10
8.6 NA 2005 Yes NA INDONESIA: SUMATERA: SW 1,313
8.6 NA 1957 Yes Yes ALASKA 2
8.6 11 1950 Yes NA INDIA-CHINA 1,530
8.6 6 1946 Yes NA ALASKA: UNIMAK ISLAND 168
8.6 NA 1938 Yes NA INDONESIA: NEW GUINEA NA
8.5 9 1963 Yes NA RUSSIA: KURIL ISLANDS NA
8.5 11 1922 Yes NA CHILE: ATACAMA 700
8.4 NA 2007 Yes NA INDONESIA: SUMATRA 25
8.4 8 2001 Yes NA PERU: AREQUIPA, MOQUEGUA, TACNA, AYACUCHO 103
8.4 NA 1933 Yes NA JAPAN: SANRIKU 3,022
8.4 11 1923 Yes NA RUSSIA: KAMCHATKA 3

The graphic below is a visualization of the previous table that includes magnitudes and deaths grouped by country. It is ordered from top to bottom in descending order of magnitude, both inside and outside of every country. The number of deaths is color coded: Cyan for the highest, light red for the lowest number, and light orange for the NA (not available) values.

At the end and in front of each bar is the magnitude value, preceded (inside the colored bars) by the number of deaths and year associated with that specific earthquake/tsunami event.

4. Deadliest earthquakes and tsunamis overall

The following table is presented in descending order by number of deaths

The 20 deadliest earthquakes/tsunamis
Year Tsunami Volcanic Magnitude Intensity Country Total Deaths
2010 Yes NA 7.0 NA HAITI: PORT-AU-PRINCE 316,000
1976 NA NA 7.5 11 CHINA: NE: TANGSHAN 242,769
2004 Yes NA 9.1 NA INDONESIA: SUMATRA: ACEH: OFF WEST COAST 227,899
1920 Yes NA 8.3 12 CHINA: GANSU PROVINCE, SHANXI PROVINCE 200,000
1923 Yes NA 7.9 NA JAPAN: TOKYO, YOKOHAMA 142,807
1948 NA NA 7.2 10 TURKMENISTAN: ASHKHABAD 110,000
2008 Yes NA 7.9 9 CHINA: SICHUAN PROVINCE 87,652
1908 Yes NA 7.0 11 ITALY: MESSINA, SICILY, CALABRIA 80,000
2005 NA NA 7.6 8 PAKISTAN: MUZAFFARABAD, URI, ANANTNAG, BARAMULA 76,213
1970 Yes NA 7.9 10 PERU: NORTHERN, PISCO, CHICLAYO 66,794
1935 Yes NA 7.5 10 PAKISTAN: QUETTA 60,000
2023 Yes NA 7.8 9 TURKEY; SYRIA 56,697
1927 NA NA 7.6 11 CHINA: GANSU PROVINCE 40,912
1990 Yes NA 7.3 7 IRAN: RASHT, QAZVIN, ZANJAN, RUDBAR, MANJIL 40,000
1939 Yes NA 7.8 12 TURKEY: ERZINCAN 32,700
2003 NA NA 6.6 9 IRAN: SOUTHEASTERN: BAM, BARAVAT 31,000
1939 Yes NA 8.3 10 CHILE: CHILLAN 30,000
1915 NA NA 7.5 11 ITALY: MARSICA, AVEZZANO, ABRUZZI 29,978
1988 NA NA 6.8 10 ARMENIA: LENINAKAN, SPITAK, KIROVAKAN 25,000
1976 Yes NA 7.5 9 GUATEMALA: CHIMALTENANGO, GUATEMALA CITY 23,000

The following is a graphic version of the previous table that includes countries, death tolls, and magnitudes. For multiple earthquakes associated with a country, they are stacked based on their death tolls, from largest at the bottom to smallest at the top. The total number of deaths is added up automatically. In turn, all countries are ordered from left to right, from highest to lowest based on their total number of deaths.

Observations from the previous two tables:

  • All except one on the list of the strongest earthquakes also involved tsunamis
  • The deadliest tsunamis/earthquakes are not necessarily the most powerful in magnitude. The deadliest earthquake/tsunami in history was 7.0 in Haiti (2010), with the highest death toll in history for an earthquake: 316,000
  • On the other hand, the most powerful in magnitude tsunamis/earthquakes are not necessarily the deadliest –location is one of the most important factors–
  • The tsunami/earthquake that occurred in Indonesia in 2004 combined a powerful 9.1 magnitude event with the second highest death toll for a tsunami/earthquake: 227,899. So, this is the only tsunami/earthquake these two tables have in common
  • The deadliest earthquake that did not include a tsunami occurred in China in 1976 with a death toll of 242,769 and a magnitude of 7.5

5. Earthquakes, number of deaths, and tsunamis per year

First and foremost, the following two visualizations reflect the GSED earthquake inclusion criteria described at the beginning, and highlighted in the full disclosure mentioned above.

Note: Each dot represents one year. And, for accuracy, the average value above has been calculated only up to the last full year.

The following visualization complements the previous one. With these two graphs we can visualize not only the number of earthquakes per year, but also their associated number of deaths per year (which also includes tsunamis caused by earthquakes) – each bar represents one year.

The only years in which no deaths were reported were 1919 and 1921. As for other years that appear to show no deaths, it is because these values are relatively small to appear on the scales used to represent them.

Note: For accuracy, the average value above has been calculated only up to the last full year.

6. Earthquakes and tsunamis by magnitude

Again, the following two visualizations reflect the GSED earthquake inclusion criteria described at the beginning, and highlighted in the full disclosure mentioned above.

One may wonder how minor and relatively insignificant earthquakes of magnitudes lower than 3.5, which are generally not felt, make it into the Global Significant Earthquakes Database. As an example, consider the 2.8 magnitude earthquake that happened on 27.Apr.2022 in Poland –A tragedy occurred at the Borynia-Zofiowka mine in southern Poland– where 10 miners disappeared after a tremor and methane gas discharge. Later, they were all declared dead.

So, we learn that even a minor earthquake that is not usually felt can trigger tragedy in some unfortunate circumstances.

The tsunami visualization above shows us the maximum water height reached for the magnitude 7 most frequent tsunamis is 15.03m.

But, to put things in perspective, these are some data on water heights in some of the most notable tsunamis:

Tsunami feature Date Country Mag Max. water height [m] Deaths
Maximum height of water recorded*** 10.Jul.1958 USA, Lituya Bay, Alaska 7.8 524 5
Both highest magnitude and number of deaths 26.Dec.2004 Indonesia 9.1 50.9 227,899
Deadliest in history** 12.Jan.2010 Haiti 7.0 3.21 316,000

Notes:

*** This tsunami was a huge splash caused by a massive landslide triggered by an earthquake.

** In this case the actual deaths attributed to the tsunami event were less than 50, and practically all the fatalities were caused by the associated earthquake. So, the deadliest tsunami in history is actually the one in Indonesia, but the deadliest earthquake is in Haiti.

Additionally, the data in the table above may be helpful in locating these events on the interactive world tsunami map in section 12.

7. Summary of earthquakes by magnitude ranges

Note: The current year death toll shows up in the summary tables heading above, at the end of section 1.

Average occurrence per year of magnitude ranges from 1900 to Last Full Year (LFY)
Magnitudes 1900-1999 2000-LFY
rare_great (mag 9) 0.03 0.09
great (mag 8) 1.04 1.00
major (mag 7) 8.20 10.22
strong (mag 6) 6.32 15.22
moderate (mag 5) 4.03 12.22
light (mag 3.5-5) 3.09 18.83
minor (mag <3.5) 0.01 0.52
NA 2.90 0.13

The figures in the previous table show an increase in the frequency of the most significant earthquakes in each magnitude range during the 21st century, compared to the 20th century.

We can also see this trend in the “Earthquakes and tsunamis per year” graph in section 5 above, specially from 2002 to 2022.

The only reduction in the frequency of occurrence is observed for the NA category; which is consistent with the findings in Appendix B: “Analysis of earthquakes without values of magnitude and/or focal depth”, where it can be seen that since around 1970, NA occurrences have decreased significantly –perhaps pointing to better overall seismic data acquisition since then–.

Thus, from the table and graph above, we see that so far in the 21st century, both the frequency of significant earthquakes, and death toll rate have increased compared to the previous century (please, see paragraph 8 in the “Acknowledgments and Final Thoughts” section at the end).

8. Correlation between magnitude and focal depth

Earth is composed of four distinct layers: The inner core (1,220 Km), the outer core (2,250 Km), the mantle (2,900 Km) and the crust (5 to 100 Km), which is what we live on.

The Earth’s crust is like the shell of a hard-boiled egg. It is extremely thin, cold and brittle compared to what lies below it. This crust ranges from 5 to 100 kilometers thick depending on oceanic versus continental crust. The thin oceanic crust is denser than the thicker continental crust. On average, oceanic crust is 6–7 km thick and basaltic in composition (basalt is a hard, black volcanic rock- it is the most common rock type in the Earth’s crust). In turn, the continental crust averages 35–40 km thick and has a roughly andesitic composition (Andesite is a type of rock formed at subduction plate boundaries. It is harder, lighter, and slightly less dense than basalt; and takes its name from the Andes mountain range in South America).

In a very general way, it is thought that the Earth’s crust “floats” on top of the soft plastic-like mantle below, as illustrated in the next figure:

So, earthquakes occur in the crust or upper mantle, which ranges from the earth’s surface to about 800 kilometers deep (about 500 miles): Shallow earthquakes are between 0 and 70 km deep; intermediate earthquakes, 70 - 300 km deep; and deep earthquakes, 300 - 700 km deep. In general, the term “deep-focus earthquakes” is applied to earthquakes deeper than 70 km. All earthquakes deeper than 70 km are localized within great slabs of lithosphere that are sinking into the Earth’s mantle (USGS Reference).

Then, the strength of shaking from an earthquake diminishes with increasing distance from the earthquake’s source, so the strength of shaking at the surface from an earthquake that occurs at 500 km deep is considerably less than if the same earthquake had occurred at 20 km depth.

However, most parts of the world experience at least occasional shallow earthquakes which originate within 70 km (43.5 miles) of the Earth’s outer surface. In fact, the great majority of earthquakes’ focal depths are shallow, and cover the whole range of the magnitude scale, which is confirmed by the graphic below:

Given that the number of earthquakes without values of magnitude or focal depth is around 19% of the total number of earthquakes analyzed, they are analyzed separately in Appendix B.

Additionally, and as a complement to this section, we can see in the graphic below that Fiji, Peru and Russia have recorded the earthquakes with the greatest focal depth as well as the largest number of them: 9, 8 and 6 respectively, with a very low fatality rate.

Any discrepancy in the count of deeper earthquakes between the two graphs above is because the latter includes earthquakes with no magnitude value (which is discussed in Appendix B), while the magnitude vs. focal depth graph does not.

9. Countries with most earthquakes and tsunamis

In the next two sets of graphics (sections 9 and 10), the first visualization is based on the earthquake dataset, which also includes tsunamis caused by earthquakes. And, the second visualization is based on the tsunami dataset (which provides more detailed data on these events). So, the first one is an overall view of earthquake and tsunami data, and the second one is a subset focused on tsunami data only.

The country with the most earthquakes since 1900 is China, with 378 occurrences and a total death toll of 651,694 (counted until December 2023); followed by Indonesia and Iran. It seems this region of planet earth experiences the most amount of earthquakes and related fatalities.

10. Deadliest earthquakes and tsunamis by country

The next two visualizations see the same previous data from a a different perspective, since it is not always true that the countries with the most amount of earthquakes have the highest death toll.

For example, Haiti, has experienced the deadliest earthquake/tsunami since 1900, but it does not show up in the previous graphics, because it has had only 7 earthquakes/tsunamis so far (until December 2023).

But, Haiti shows up in the following two graphics and also alternates with China in the first two places because it is second in earthquake fatalities, but first in tsunami fatalities. That is because of the 2010 earthquake/tsunami that caused the highest number of deaths for a single earthquake/tsunami event since 1900: 316,000.

And, this is something to highlight:

  • Japan has experienced 220 earthquakes and tsunami events combined from 1900 to December 2023, in the magnitude range of 4.9 up to 9.1 (in 2011) with 187,280 total fatalities. On the other hand,
  • Haiti has suffered 7 earthquake and tsunami events combined in the same period but with 318,276 fatalities.

This is to say that Japan has had 31.4 times more earthquakes and tsunamis combined than Haiti, but with 59 % of Haiti’s fatalities only.

Perhaps these figures just reveal the overwhelming difference between two extreme economies: A rich and developed country, with the knowledge, experience, resources, and discipline to deal with frequent earthquakes/tsunamis on the one hand; and an underdeveloped country, lacking everything, and mired in poverty at the other extreme. We see how differently they fare in the face of these natural disasters.

Note: For a clarification on Haiti in the visualization below, please see the tsunami table and related notes at the end of section 6 above.

11. Interactive world map for the earthquake dataset, color coded, and with magnitude filters

The interactive world map below offers the option to filter earthquakes by magnitude, and is also a very useful source of information. By clicking on each circle that represents an earthquake the user can get data on magnitude, intensity, volcanic eruption (if any), date, and total deaths.

On this map individual earthquakes are represented by color coded circles following this pattern:

  • 9.0 - 9.9 ==> Cyan
  • 8.0 - 8.9 ==> Magenta
  • 7.0 - 7.9 ==> Red
  • 6.1 - 6.9 ==> Maroon
  • 5.5 - 6.0 ==> Dark Orange
  • 1.6 - 5.4 ==> Blue
  • NA (earthquakes with missing magnitudes) ==> Gray

On the top right corner there is an icon (showing stacked layers) –Hovering over it (or touching it) displays magnitude check boxes to filter earthquakes by selected magnitudes. To exit just move the cursor or tap outside the box.

There are two ways to zoom in and out, either by using the “+” and “-” signs on the top left, or by scrolling up and down with the mouse wheel in the area map. Using any of these methods will zoom in/out in gradual steps, rather than directly clicking or tapping in a cluster, which will cause a bigger zoom in/out. To scroll up and down the page, just move the cursor outside the map. You can also click and drag to move the map in any direction.

The map also groups the earthquakes on each magnitude layer in clusters that depend on the zoom level, and adjust themselves automatically to show the number of earthquakes grouped in each cluster. In this way the earthquake’s visualization doesn’t look too crowded.

Hovering over (or touching) a colored circle displays a label containing the date, magnitude, and the text “more…”. Clicking (or tapping) on it will open a text box containing magnitude, intensity, volcanic eruption (if any), date, and total deaths. To close this box, you can click (or tap) on the “x” inside the box, or just click (or tap) outside.

The displayed date follows the format dd/mm/yyyy.

Note: For the next two visualizations, clusters group events with the same magnitude ranges only (same color). In the event that several earthquakes of different magnitude ranges share the same latitude and longitude coordinates, they overlap each other. In this case, it is better to uncheck the magnitude ranges to visualize them only one at a time. In turn, clicking on a cluster will cause all events to be displayed as ‘spider legs’ radiating from the common coordinates.

12. Interactive world map for the tsunami dataset, color coded, and with magnitude filters

This is some general information about tsunami events:

  • “Tsunami” is a Japanese word meaning “harbor wave”. The global distribution of these events is 70% Pacific Ocean, 15% Mediterranean Sea, 9% Caribbean Sea and Atlantic Ocean, and 6% Indian Ocean.

  • Major tsunamis occur in the Pacific Ocean region only about once per decade.

  • Volcanoes have generated significant tsunamis with death tolls as large as 30,000 people from a single event.

  • The major part of the tsunami energy is transmitted at right angles to the direction of the major axis, both toward the near shore and along a great circle path toward the shore on the opposite side of the ocean. Thus, tsunamis in Chile have severe impact on Japan; and those in the Gulf of Alaska on the west coast of North America.

Below there is a description of the terms associated with tsunamis which are provided in the world wide interactive map:

Earthquake magnitude - If there is any associated earthquake.

Tsunami intensity - Measured based on the maximum water height.

Number of deposits - A tsunami deposit (the term tsunamiite is also sometimes used) is a sedimentary unit deposited as the result of a tsunami. Such deposits may be left onshore during the inundation phase or offshore during the ‘backwash’ phase.

Volcanic eruption - If there is any associated volcanic eruption.

Event validity - It takes values from -1 to 4, coded as follows:

  • -1 = Erroneous entry (not considered in the analysis)
  • 0 = Event that only caused a seiche/disturbance in a river. A seiche is also a temporary disturbance or oscillation in the water level of a lake or partially enclosed body of water
  • 1 = Very doubtful tsunami
  • 2 = Questionable tsunami
  • 3 = Probable tsunami
  • 4 = Definite tsunami

If a tsunami shows up inland, the first thing we need to check is its validity numeric value. It could just be a seiche (validity = 0), or a very doubtful tsunami (validity = 1).

Cause code - It takes values from 0 to 11, and shows 11 possible causes for a tsunami as described below:

  • 0 = Unknown Cause
  • 1 = Earthquake
  • 2 = Questionable Earthquake
  • 3 = Earthquake and landslide
  • 4 = Volcano and earthquake
  • 5 = Volcano, earthquake and landslide
  • 6 = Volcano
  • 7 = Volcano and landslide
  • 8 = Landslide
  • 9 = Meteorological
  • 10 = Explosion
  • 11 = Astronomical tide

Maximum water height or Run-up - The large amount of water that a tsunami pushes onto the shore above the regular sea level is called run-up, that is the maximum vertical height onshore above sea level reached by a tsunami. Run-up is the more damaging force than the huge tsunami waves as it surges inland and destroys all in its path.

Two other terms may be determined from the run-up value: (1) tsunami magnitude Iida, and (2) tsunami intensity. In this map, only the intensity is provided because of the amount of data available for it.

Number of run-ups

Date (dd/mm/yyyy), and

Total deaths

By clicking on each circle that represents a tsunami, the user can get information based on the data listed above: Earthquake magnitude, tsunami intensity, number of deposits, volcanic eruption (if any), event validity, cause code, maximum water height, number of run-ups, date (dd/mm/yyyy), and total deaths.

The same color coding and instructions for use as the previous map apply to this one. And again, clusters are for events that share the same color-coded range of magnitudes only.

Acknowledgments and Final Thoughts

This work was inspired by the capstone project I undertook to obtain the “Google Data Analytics Professional Certificate”, offered on the online learning platform Coursera. All programming work was done using the “R” programming language in the RStudio environment. I have really enjoyed programming in this powerful language built for data analysis, and I am indebted to its talented online community.

I also want to express my appreciation to NOAA for making available the public earthquake and tsunami datasets, and for answering my questions when I contacted them –NOAA does a great job collecting, validating and presenting associated socio-economic data on these powerful forces of nature–.

And, it is also very important that earthquakes and tsunamis are continuously studied and monitored since there is still much to learn about them, and they are very complex events.

True, earthquakes, tsunamis and volcanic eruptions are among the most powerful events in nature, with terrifying destructive power, and enormous potential impact in loss of human life, so much that historian Will Durant was compelled to write: “Civilisation exists by geological consent subject to change without notice”.

But, as powerful and life-threatening as these geological events can be, it is agreed that much can be done to reduce their death toll, with sufficient political will, knowledge and cooperation both internally and externally in the affected countries.

To start, safe housing must be treated as a human right –the ‘where’ to build and ‘how’ to build are crucial– because not only are populations in high-risk areas increasing dramatically, but earthquake-proof building codes are being bypassed. And, the sad truth is that collapsing buildings kill people, not earthquakes –but every building that stands saves lives–. It has also been found helpful to implement effective emergency procedures and advance warnings –as far as possible– as Japan does.

Likewise, it is equally true that poverty, inequality, greed, and bad government administrations among other factors prevent the implementation of these life-saving measures, thus greatly magnifying the loss of human life –as previously pointed out when comparing the effects in Japan and Haiti–.

Perhaps, the reasons cited above have contributed to the fact that fatalities due to earthquakes and tsunamis during the 21st century (until 2023) show the figure of 888,868 (from section 7); which represents more than half (55%) of the total of the 20th century (1,602,776) –in just 23 years–.

And, in the same spirit of data analysis, I try to put some data into perspective in the table below:

Event Estimated Fatalities
Earthquakes and Tsunamis during the 20th Century 1,602,776
Deaths by War and Oppression during the 20th Century Over 203 million
Tobacco Epidemic Worldwide each year Over 8 million

Here, we can see that the total death toll from earthquakes (and tsunamis caused by earthquakes) pales in comparison to the deaths caused by man, both to themselves and to others: The fatalities caused by earthquakes during the 20th century is 0.8 % of the deaths caused by war and oppression in the same period of time. And, what’s worse, tobacco smoking deaths in one year are 5 times the deaths from earthquakes in the entire 20th century or, what is the same, the number of deaths in a century of earthquakes occurs about every 2.4 months on average, due to tobacco.

Undoubtedly, these facts are certainly food for thought.

But all things considered, let us never forget that Earth remains a uniquely beautiful jewel, “a fragile miracle of life that wanders blue in the infinite blackness of space. Precious beyond all comparison. Sacred in its wondrous possibilities”, as heartfelt expressed by Dean Francis Sayre.

These possibilities are something to be dreamed of. However, individually, we have a choice of what we do, and these possibilities start from within: A world with no wars and violence, and where there is more equality. A world without government corruption and greed. A world where human life is considered of the highest value –where people take care of each other–, and respect nature and the environment.

It is also worth noting that the GSED earthquake/tsunami dataset not only provides figures for the reported deaths, but also for people injured and missing (although this last data is scarce and uncertain, and do not really add up to much), houses damaged, houses destroyed, and the total cost of damage in US dollars. But, I have not touched any of these statistics so as not to lengthen the current analysis; and for considering that human life is of the utmost value, which cannot be recovered nor can an estimated value be put on it.

But at the same time, the GSED data set can be subject to constant modifications due to new data that has come to light for any event in history.

Besides, I have not commented on all the details exposed in this analysis to avoid making it too long to read, but each person may draw their own additional insights from here. The intent is to provide useful and up-to-date seismic data in a manner that is accessible and easy to follow. After all, this analysis project is intended to be just a sample of the curiosity-driven data analysis applied to the NOAA earthquake dataset.

Finally, any suggestion, or any other query that is not included in this analysis, I am open to consider it ().

Thank you for reading it!

Appendix A

This appendix shows in detail the Modified Mercalli’s Intensity Scale. The intensity is the measure of shaking at each location, and this varies from place to place, depending mostly on the distance from the fault rupture area. It is based solely on observable earthquake damage.

Modified Mercalli Intensity (MMI) Scale:

Scale Level Ground Conditions
I. Not felt Not felt except by very few under especially favorable conditions.
II. Weak Felt only by a few people at rest, especially on upper floors of buildings. Delicately suspended objects may swing.
III. Weak Felt quite noticeably by people indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations are similar to the passing of a truck, with duration estimated.
IV. Light Felt indoors by many, outdoors by few during the day. At night, some are awakened. Dishes, windows, and doors are disturbed; walls make cracking sounds. Sensations are like a heavy truck striking a building. Standing motor cars are rocked noticeably.
V. Moderate Felt by nearly everyone; many awakened. Some dishes and windows are broken. Unstable objects are overturned. Pendulum clocks may stop.
VI. Strong Felt by all, and many are frightened. Some heavy furniture is moved, a few instances of fallen plaster occur. Damage is slight.
VII. Very Strong Damage is negligible in buildings of good design and construction; but slight to moderate in well-built ordinary structures; damage is considerable in poorly built or badly designed structures; some chimneys are broken. Noticed by people in driving motor cars.
VIII. Severe Damage slight in especially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. Sand and mud ejected in small amounts. Changes in well water. People in driving motor cars are disturbed.
IX. Violent Damage is considerable in especially designed structures; well-designed frame structures are thrown out of plumb. Damage is great in substantial buildings, with partial collapse. Buildings are shifted off foundations. Liquefaction occurs. Underground pipes are broken.
X. Extreme Some well-built wooden structures are destroyed; most masonry and frame structures are destroyed with foundations. Rails are bent. Landslides considerable from river banks and steep slopes. Shifted sand and mud. Water splashed over banks.
XI. Extreme Few, if any, masonry structures remain standing. Bridges are destroyed. Broad fissures erupt in the ground. Underground pipelines are rendered completely out of service. Earth slumps and land slips in soft ground. Rails are bent greatly.
XII. Extreme Damage is total. Waves are seen on ground surfaces. Lines of sight and level are distorted. Objects are thrown upward into the air.

Correlation of the Modified Mercalli Intensity (MMI) scale with the Magnitude scale

Magnitude Typical Maximum MMI Intensity
1.0 - 3.0 I
3.0 - 3.9 II - III
4.0 - 4.9 IV - V
5.0 - 5.9 VI - VII
6.0 - 6.9 VII - IX
7.0 and higher VII or higher

Appendix B

Analysis of earthquakes without values of magnitude and/or focal depth

The following two visualizations break down the number of these earthquakes separately. To compensate for the lack of one of these values, the year of occurrence has been chosen to plot them instead. And, there are also 240 earthquakes without magnitude and focal depth (see the bar graph below). However, they (and the other earthquakes without magnitudes) may well have intensity values on the Modified Mercalli’s scale.

What’s interesting about the two graphs above is the frequency of these events from 1970 onwards: 15 in the first case and 2 in the second.

Also, curiously, the same pattern appears in the visualization of the number of earthquakes per year for the 240 events without magnitude and focal depth, which shows only 3 events from 1968 to 2022 (see the bar graph below). That makes a total of 20 events, or 2.7% of the total events (~750) without magnitude or focal depth from 1900 to 2022 (Remember that this is for the earthquake dataset which contains tsunamis caused by earthquakes only, but the tsunami dataset also contains tsunamis not caused by earthquakes, which do not have magnitude and focal depth data).

So, we can see the stark contrast between the 2.7% of these events registered in the 52-year period from 1970 to 2022, with the remaining 97.3% of them in the earlier 70-year period from 1900 to 1970.

Therefore, it appears that since around 1970 the acquisition of seismic data has somehow improved significantly.

–arl–