Icons

Earthquakes Yearly Average Magnitude 6+ (1900–2013)

Overview

source: Magnitude 6+ Earthquakes All recorded earthquakes with a magnitude of 6 or greater from 1900–2013. Source: United States Geological Survey (USGS)

• https://public.tableau.com/app/learn/sample-data
• https://earthquake.usgs.gov/earthquakes/search/

library(readxl)
raw_data <- read_excel("data/Mag6PlusEarthquakes_1900-2013.xlsx")
View(raw_data)

library(tidyverse)
library(sf)
library(rnaturalearth)
library(ggflags)

data_sf <- raw_data %>%
  janitor::clean_names()%>%
  select(date,time=time_2, latitude,longitude,
         depth,mag) %>%
  drop_na() %>%
  mutate(year =year(date),.after=date) %>% 
  group_by(year, longitude, latitude) %>%
  reframe(avg_mag=mean(mag)) %>%
  st_as_sf(coords = c("longitude","latitude"),crs=4326)

world_coastline <- rnaturalearth::ne_coastline()

ggplot() +
  geom_sf(data = world_coastline) +
  geom_point(data = raw_data, aes(x=longitude,y=latitude), 
             size = 2,
             shape = 21, stroke=0.1, color="grey80") +
  geom_sf(data = data_sf,shape=".",color="red") +
  ggthemes::theme_map()

continents <- ne_download(scale = "medium",
                          type = "geography_regions_polys",
                          category = "physical",
                          returnclass = "sf") %>%
  janitor::clean_names() %>%
  filter(featurecla == "Continent") %>%
  select(name, geometry)

# centroid
continents_centroid <- continents %>%
  mutate(centroid = st_centroid(geometry))

coords <- st_coordinates(continents_centroid$centroid)
continents_centroid$lon <- coords[,1]
continents_centroid$lat <- coords[,2]

continents_centroid$flag <- c(
  "SOUTH AMERICA" = "br",   # Brazil
  "AUSTRALIA"     = "au",   # Australia
  "AFRICA"        = "za",   # South Africa
  "ANTARCTICA"    = "aq",   # Antarctica flag exists in ggflags
  "ASIA"          = "jp",   # Japan
  "EUROPE"        = "eu",   # EU flag
  "NORTH AMERICA" = "ca"    # Canada
)[continents_centroid$name]

ggplot() +
  geom_sf(data = world_coastline) +
  geom_point(data = raw_data, aes(x=longitude,y=latitude), 
             size = 2,
             shape = 21, stroke=0.1, color="grey80") +
  geom_sf(data = data_sf,shape=".",color="red") +
  geom_flag(data = continents_centroid,
            aes(x = lon, y = lat, country = flag),
            size = 10) +
  labs(title = "Earthquakes Yearly Average Magnitude 6+ (1900–2013)",
       subtitle = "Continents Centroid marked with Flag Icons",
       caption = "#30DayMapChallenge 2025 | Day 21 Icons\nData: United States Geological Survey (USGS) | Map: Federica Gazzelloni") +
  ggthemes::theme_map()

ggsave("day21_icons.png", width=6,height=4, dpi=320,bg="white")